In most F2P games with a cash shop, the items you buy with cash are usually nicer looking then the ones you get "free" in-game. They know that you are more likely to spend more money on an item that looks good, them on an item that looks like crap. If you want to get an idea of how a very successful F2P company runs their cash shop take a look at pretty much any game from PWI. Perfect World itself is the golden standard for F2P MMOs, they have been around for a long time, still have a very large population (hundreds of thousands of players if you count the asian servers). Or look at another one of their F2P games Blacklight Retribution and look at their cash shop. Now look at their weapon models, and armor models. They are all modular, so not very resource intensive, now add the skins you can get and you have a pretty nice customizeble weapons that look really really good. In F2P games where you generate money by people's willingness to spend money, you really need to make sure your stuff looks good, so they even buy something that is not even an upgrade but it looks much better.