I think overall the prices are better than other places... but then again I really only purchase the new books that come out right at $9.99.
There is a guy here that did a price comparison between Amazon and fictionwise and fictionwise was cheaper.
https://www.mobileread.com/forums/showthread.php?t=67635
I like to have my book at Amazon and have the ability to use wispernet... but that is just my $0.02