Beyond Shopify: The Total Cost of Ownership (TCO) of Scaling on Open-Source Architecture in 2026

Most brands that pass £5 million a year on Shopify hit the same moment. The monthly bill is no longer a line item you ignore. There is the Plus fee, a stack of app subscriptions, and a 0.2% cut on every sale if you use your own payment processor. Someone on the team asks the obvious question: would it be cheaper to run our own store on WooCommerce or OpenCart?

The honest answer is that open-source software is free, but running it is not. This article breaks down what a £5M store actually pays on Shopify Plus in 2026, then lists the costs that appear once you own the platform: hosting, security, developers and plug-ins. It ends with a three-year cost table and a plain view of which businesses gain from the move and which do not.

What a £5M store pays on Shopify Plus

Shopify Plus starts at $2,300 a month on a three-year term, or $2,500 a month on a one-year term. Shopify bills Plus in US dollars, so at September 2026 exchange rates that is about £1,740 to £1,890 a month, or £20,900 to £22,700 a year before you sell anything. Once monthly sales pass roughly $800,000 (about £600,000), Shopify moves many merchants to a variable fee instead. Shopify does not publish that rate, and industry reports put it between 0.25% and 0.40% of sales. A £5M store sells about £417,000 a month, so it usually stays on the flat fee for now.

Payment fees come next. Shopify does not publish its Shopify Payments rates for Plus, and UK brands at this size negotiate them. For a reference point, Stripe’s standard rate for UK cards is 1.5% plus 20p. If you prefer your own processor, such as Adyen or a bank you already use, Shopify adds 0.2% per transaction. On £5 million in sales, that extra charge is £10,000 a year.

Apps are where the bill grows quietly. Plus brands commonly spend about £750 to £3,800 a month on apps for subscriptions, bundles, search, loyalty and reviews. Some of those tools, like email marketing, you would pay for on any platform. Others exist only because Shopify does not do that job itself, and those are the ones an open-source store can replace.

Hosting and infrastructure

On Shopify, servers are someone else’s problem. On WooCommerce or OpenCart, they are yours. A £5M store with sale-day spikes needs more than a £25 shared plan. Managed WooCommerce hosts such as Pressable list premium single-site plans from $350 a month (about £265), and most stores at this size add a staging copy for testing updates. A cloud setup on AWS or a similar provider costs about the same once you include backups and database servers. Put a CDN and firewall in front of it, like Cloudflare Business at about £150 a month on annual billing, and a realistic budget is £550 to £750 a month. The larger cost is the planning. Someone has to check that the server can handle Black Friday before it arrives, not during it.

Security and PCI compliance

Shopify is a PCI DSS Level 1 service provider, so card security is mostly handled for you. When you self-host, the store and the server become part of your compliance scope. Most merchants keep that scope small by using hosted payment fields from Stripe, Braintree or Adyen, so card numbers never touch their server. You still have to patch WordPress, WooCommerce and every plug-in quickly, because attackers scan for known holes within days of a fix going public. Budget for malware scanning and off-site backups at around £75 a month. Add a yearly penetration test and quarterly vulnerability scans, which often run about £3,800 a year for a store this size. A single skimming incident on the checkout page costs far more than any of this, once you add refunds and card-scheme fines.

Developers and ongoing maintenance

This is the line most founders underestimate. WooCommerce ships updates about once a month, and WordPress and PHP move on their own schedules. Each update needs testing on staging before it goes live, because one plug-in conflict can break checkout on a Saturday morning. Experienced WooCommerce developers charge about £75 to £150 an hour, and agencies offer maintenance retainers for large stores at £1,500 to £2,300 or more a month. OpenCart has a smaller developer pool and fewer ready-made extensions, so more of the store ends up as custom code. That usually means paying a little more per month and depending on fewer people who know your setup. Shopify Plus stores still pay developers for theme and app work, but they do not pay anyone to keep the platform itself running.

Plug-in dependency costs

Leaving Shopify does not end plug-in spending. It changes its shape. WooCommerce extensions are sold as yearly licences, such as WooCommerce Subscriptions at about £210 a year or AutomateWoo at about £120 a year. A large store with ten to twenty paid plug-ins often spends £2,300 to £3,800 a year, which is much less than a Shopify app stack. The hidden cost is dependency. When a plug-in author stops updating their code, you either pay a developer to take it over or rebuild that feature. OpenCart extensions are usually one-time purchases, which looks cheaper, but many are sold by solo developers and are not always updated for new OpenCart versions. Before migrating, list every app you use today and check that each has a maintained open-source match.

API limits and control

Shopify’s GraphQL Admin API gives Plus stores 1,000 cost points per second, ten times the standard plan. That is enough for most order syncs and stock updates. It starts to pinch when an ERP pushes price changes across tens of thousands of variants, or when several apps compete for the same budget during a flash sale. Checkout changes are also limited to what Shopify’s Checkout Extensibility allows. WooCommerce and OpenCart have no platform-imposed rate limit. WooCommerce’s Store API rate limiting is off by default, so the real ceiling is your own server. You can also rewrite checkout and pricing logic yourself, down to the database. That freedom is the main reason large brands move, but every custom change is code your team has to keep working through future updates.

Three-year cost comparison at £5M a year

The table below models a UK store with £5 million in yearly sales and about 50,000 orders a year. It leaves out costs that are the same on every platform, such as card processing on Shopify Payments or Stripe and your email marketing tool. Figures are estimates in pounds, excluding VAT, based on published 2026 pricing and typical agency rates. Shopify, Cloudflare and most plug-in sellers bill in US dollars, so those lines are converted at about $1.32 to the pound (September 2026) and will move with the exchange rate.

Two things change these numbers. If you use your own payment processor on Shopify, add £30,000 for the 0.2% fee, which puts Plus at £166,440. And on an open-source store you can negotiate processing rates freely. Saving 0.3 percentage points on £5 million is £15,000 a year, or £45,000 over three years.

Migration costs and who should move

The move itself is the biggest single bill. Agencies commonly quote from about £40,000 for a simple catalogue to well over £110,000 when ERP links and custom checkout rules are involved. Plan for URL redirects and a few weeks of lower search traffic while Google re-indexes the new store. On the table above, WooCommerce only pulls ahead of Shopify Plus in running costs, and the migration takes more than three years to pay back on fees alone. The math improves if you already pay the 0.2% gateway fee or your app bill is well above £900 a month. The case gets stronger still when Shopify’s limits block something you need, like complex B2B pricing or a heavily custom checkout. It also helps to have a developer or agency you trust before you start. A brand that sells a simple catalogue and has no in-house tech lead will usually spend less, and sleep better, staying on Plus.

Conclusion

At £5 million a year, open source is not the easy cost cut it looks like from the Shopify invoice. The licence fee disappears, but hosting and a monthly developer retainer take its place, and the migration bill can wipe out three years of savings. WooCommerce is the safer open-source choice because of its larger developer pool and regular updates. OpenCart can cost less to host but asks more of your developers. Move when you need control Shopify will not give you, or when your fees and apps are well above the numbers in this table. Before deciding, price your own app list and payment rates line by line, since those figures decide the outcome more than the platform name does.

Sources

• Shopify Plus pricing
• Shopify API rate limits
• Shopify Plus pricing guide, Ringly
• Shopify Plus pricing guide, BrokenRubik
• Shopify Plus total cost of ownership, Ask Phill
• WooCommerce Store API rate limiting
• WooCommerce pricing breakdown, Swell
• WooCommerce development costs, Codeable
• Pressable hosting plans
• Cloudflare plans
• Stripe pricing
• Stripe UK pricing
• GBP/USD exchange rate, Trading Economics