I used to charge £500-£1000 for a website design and build 10 year's ago, as a freelancer. It's just not viable these days. I now run a small digital agency in west London, and we provide bespoke web design, WordPress builds, bespoke functionality where required, and on-page SEO starting at £3,500. The price goes up, if the client requires more than one design to choose from, or if they need really bespoke functionality that a plug-in won't provide. We'll also bill by the hour if there's any scope creep involved.
Where we really stepped up our game was being able to provide website maintenance, on-going SEO, and paid ads management, as part of a retainer.
As other's have mentioned a good way to judge what to charge for a website is to understand who the client is, what their product or service is, and how much their product or service is worth as a sale to them. Then look at the value you can give their business with a good website design, that does what they need, and gets them conversions.
FYI, the agency I used to work for 15 years ago (before I went solo), used to do websites for £5000 back then. They now do them for £50,000 minimum.