a different amount of revenue for these sites

so using value based pricing....one would charge based on the revenue that the site is expected to generate (or increase if it is a re-design).

pricing this way requires dialog with the client .... basically probing them to find out the purpose of their site...and the expected outcomes...(i.e i want to increase my online sales by 10%...i want to generate xyz amount of subscribers) which is something you should be doing anyway since the purpose of a website is to solve a problem.

then continue the discussion to figure out the value that outcome will likely produce for them and then pitch your price based on that.

if they expect $50,000 in revenue generated from the site...then 10% of that is no big deal....and as the expected revenue increase so does the cost of the site since the value of the site increases as well

so yeah....this type of pricing model gets you away from pricing based on hours...or how much work it takes to build a site....there are only so many hours in a day...if you are basing your price on hours alone then you are creating a cap in your potential income....there is only so high an hourly rate a client will accept based on the market. value based pricing allows you to increase your hourly rate without increasing your hourly rate :)