A working UK ecommerce site costs between £2,000 and £6,000 to build for most small and mid-sized businesses, plus £30–£150 a month to run. Above that you're paying for integrations, not prettier pages. Anyone quoting an online shop without first asking how many products you have is guessing, and their number will change later.
Why product count drives the price
Design effort barely moves between a 20-product shop and a 2,000-product one — it's the same templates. What moves is everything around the products: how the catalogue is structured, whether variants exist (size, colour, material), how stock syncs, how you get the data in, and how a customer finds one item among two thousand.
Twenty products can be typed in by hand in an afternoon. Two thousand needs a feed, a mapping exercise and a way to keep it current. That's the gap, and it's the question to ask any agency early.
Shopify, WooCommerce, Magento
Shopify — fastest to launch, hardest to outgrow badly. From roughly £25 a month plus transaction costs, hosting and security handled for you. The trade-off is rent: you pay monthly forever, and deep customisation fights the platform. Right for most businesses selling straightforward products who want to be trading in weeks.
WooCommerce — WordPress with a shop attached. No platform fee, total control, your data. In exchange you own the hosting, the updates and the security. Right when you already run WordPress, when you need unusual product logic, or when monthly fees over five years genuinely outweigh maintenance.
Magento (Adobe Commerce) — genuinely powerful, and overkill for almost everyone reading this. Multi-store, multi-currency, complex B2B pricing. If you don't have a developer on retainer, this isn't your platform, whatever the agency proposing it says.
The costs that show up after launch
Payment processing takes roughly 1.4%–2.9% plus 20p per transaction depending on card type and provider. Platform fees if you're on Shopify. Hosting, if you're not. Product photography, which is the single most underestimated line and the one that most affects conversion. And someone to keep the catalogue accurate — a shop with wrong stock levels loses customers faster than an ugly one.
Where the money is genuinely worth spending
Product photography, checkout simplicity, and the search box. In that order. A gorgeous homepage does very little; customers arrive on product pages from Google and leave at checkout. Every field you remove from checkout measurably increases orders, which is why the good platforms keep removing them.
What we won't do
We won't build a 500-product shop for a business that has never sold online. Start with your best 30 products, learn what actually sells, then expand the catalogue with evidence behind it. Building the full range first is how businesses spend £6,000 discovering that four products account for most of the revenue.