The tiers, honestly described
Under £1,000 buys a template with your logo and words poured in. £2,000 to £6,000 buys a well-executed template or a simple custom build with someone actually thinking about your customers. £8,000 to £20,000 buys genuine design, custom development, SEO foundations and content work. Beyond that, you're into ecommerce complexity, integrations and platforms.
What actually drives cost
Thinking time. Anyone can install a theme. You're paying for someone to understand what makes your business worth choosing and to build the site around that. Also: content (someone has to write it), photography, ecommerce plumbing, and the technical SEO that decides whether Google ever sends you anyone.
The trap in the middle
The worst value in the market is template work sold at custom prices: £8,000 for a theme you could identify on three other sites. Ask any Sheffield web agency two questions. Is this a theme or custom? And can I see the last three sites you built? The portfolio answers what the sales call won't.
Spend where it returns
A £3,000 site that loads fast, ranks for your services and takes enquiries beats a £15,000 art piece that does none of it. Judge the quote against the job the site must do, not against how expensive it looks.