Sometimes you get what you pay for (in quality) and sometimes they are just *really* proud of their logo or the brand.
I've bought cheap jerseys and expensive jerseys and have fallen apart quickly. I've also had cheap jerseys and expensive jerseys last for years.
I stopped buying jerseys a few years ago. I just buy normal shirts that can be worn both on the bike and when I run. I do an equal amount of both sports. I bought a fairly big Bento box for the bike so I don't need the pockets to carry things anymore.