I actually think $300 and $400 is rather cheap when you're dealing with businesses. And yes, that's just for a logo. You're not charging simply for a logo design, but for the experience as well. Too many young designers look at a simple logo and think, "I could do that." Maybe, but a lot more goes into it than just designing something cool. With logo design, comes inherent complexity and attention detail. Treatment of type, color decisions, iconotypes, etc, make logo design an art unto itself.

Sure, I've designed the quick and easy web logo for much, much cheaper. But, I take all of the above into consideration.