Ever watch the tv show "pawn stars"? At least once an episode there's some guy - with no idea about what he has - walk in with an idea that they're going to sell some piece of trash for $5,000. When the bosses actually look at the piece, they offer $100. the guy leaves the shop hurt because "it's gotta be worth more than that", in spite of the fact that they don't know antiques or don't know how to run a basic business.

Same thing I think happens with programming. "I have this idea, and I know (somehow) that $500 is a fair price, in spite of the fact that they are neither technical people or... ever commissioned custom development before".

So, it's not just software development...