As a system admin, what do you do when someone comes to you and says "how much hardware do I need to support my application?" Imagine trying to give them the correct answer without being able to talk to them.
as another poster said, when you're just starting to compile a list of options, high pressure sales pitches are a turn off.
In my experience, the fastest way to lose a prospect is by being ambiguous or flighty about the price which is exactly what you'd be doing if you posted ballpark figures on your site (as well as inviting lots of questions and raised eyebrows since our installations literally range from $1000-$25000)