What you need to realize:
Blizzard does not hire a new team to create premium items, they have old workers create them. What happens when people are spending more time on one thing and less on another? One of those things goes down in quality. Or, are we going to fool ourselves and assume that everyone is spending more time working to be able to create the same amount of "free" content along with premium items?
You get frustrated because people don't get it? It's not quite so simple.