Well, that is the million dollar question. Surely there should be some way of regulating the cost and an explanation why one designer charges ten time more than the other.
The more important question is - Is it really the same result? You can have 2 websites looking 99.9% the same, but how well does the functionality of each one work? Is the website properly optimized for search engines? see search engine optimization Will one of the designers disappear after a year when you need updates done on your site. Do both offer the same support you expect. Is the site written in the same language as to your requirements. Does both websites load at the same speed or does it take forever?
Now hold on, I'm not saying that a more expensive web designer is always better, but what I am saying is that there can be some clear distinctions between them and not meaning that the more expensive designer will always offer the better service. Look at the designer's portfolio and how long they have been around. Are they specialists in your requirements etc. Request a Quote