I work closely with two design companies in that while I'm not their manager, I play management roles when it comes to how the business operates. One strict rule that I have is that quotes are ballpark figures which will go up or down. If a client wants a detailed quote, that takes time, and that costs money. In my experience they're happy to pay for the quote or if they choose to go through the design process with the company then that price is absorbed into the design price as a credit (so the quote is essentially free).
Time is money, it's ALWAYS money. Granted, we're not dealing with the guy that wants a design from scratch for $500, we're dealing with a different base of clients, but they're the market that we are after. Those in the busienss with the money needed to hire our services have no problem spending the $75 or $100 on a quote.
I'm also a believer in the NO-SPEC (do not do sample designs on spec work). http://www.nospec.com
for more information. You'll see at the bottom of the page that Hands-on believes strongly in this frame of thinking and we provide the hosting to their organization. NEVER do work without being paid for your ideas.