If prisms are as easy to make as you say, then you can make a nice amount of gil by making a lot. I don't know about your server, but they're going anywhere from 4k to 20k on mine. Having them easy to craft makes them more accessible to players, and less people would buy them if they didn't feel the need to pay an arm and a leg to change how a certain part of their equipment looks. Also, it's a pretty convoluted system already, let's not make it worse by having to get a crafter apply a glamour.