Theres a lot of stuff that can raise the price of a PSU. I'm no expert on them, but any PSU from a reputable company will perform to its specifications.
Rosewill is one of the best, IMO, so if you like that, go with it. The more expensive PSUs have other features that are pretty much unneeded to most people, but all the good ones have the basic safety features that you can expect from a PSU.