It's NOT a ****ing investment!!!! It's a price, a fee, a charge, but NOT an investment. An investment is something that provides a return on capitol. If someone can please explain how a photograph does that (other than of course those one-in-a-million shots that make the cover of NG, NYT, etc), I would love to know, because I should be a millionaire many times over.
To answer your question however, I charge a flat rate for almost all of my work, and that's clearly displayed on my 'site. I've thought about both sides of the "I want to know" and "If you need to ask you can't afford it" argument, and as someone who wants to know up front how much things are going to cost, it would be hypocritical not to provide that information to potential clients.