The only good counter-argument for this feature in this game is that crafted gear is not garbage and it's permanent (no full loot/gear destruction). This means if you can essentially buy the carrot on the stick and end up with not much to do in terms of gear progression unless you're a savage raider.

That said, I think it would be a decent idea to be able to sell the job level boosting stuff so that people who have disposable gil but not a ton of disposable cash can have the opportunity to skip levels as well.