Something like what your describing isn't a bad idea at all. The problem becomes that with that kind of system you actually will have more rewarding content but ultimately less content. In a game that already struggles to have things to consistently do this is a bad thing.
Also, add to boot that most people will stop gathering meaning that crafters will corner the market and then we have a whole new problem on the opposite end of the spectrum.
Honestly, this whole conversation is starting to border on people either being free market or not. Besides, what the hell are people even going to spend gil on right now?
