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.
There doesn't have to be anything high pressure about it. When someone calls me for a quote I simply ask them for the details I need and tell them exactly what it will cost.
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)
Even the information that your installs cost $1-25k is useful and shold be on your website. We can all understand ranges of options. That tells me it doesnt cost $1m, lets me know who I will need to get approval from, and most people will know roughly where in the range thy are.
"Based on previous builds of similar applications you'll need at least <X>. When you have a better idea of your requirements let me know and I can give you a better idea of the hardware requirements"
as another poster said, when you're just starting to compile a list of options, high pressure sales pitches are a turn off.