Take Drupal for example - cheap AND good. Compare with our new Mega Corp CMS which had a 7 figure price tag and a work flow so atrocious it had to be scrapped before deployment was complete.
If you want good products then by picking something that is already good and only requires minor changes you have a pretty decent chance at a fair price (which might be high or low).
http://buytaert.net/drupal-usability-testing
It went through a usability test and surprise, surprise, the whole Drupal nomenclature is actually off-putting for the average Joe.
Usability is difficult. Very difficult. We'll see the fruits in Drupal 7/8. As a programmer/hacker/ia/ui guy -- I find all fascinating.
The general trend I think is UI is beginning to come of age.
to a point. While design can often have a rang of price there can be a clear difference between paying some one a living wage and not. This number can vary international but it's good to know what is considered a professional wage abroad.
Also price can have a high correlation to experience. More experience is good if you care about the details but many rather stay cheap.
the design field is changing and there is a lot of price fluctuation and it can be hard as a company to gauge if a company is worth the price. But to say there is little correlation is a little misleading.