Well, yes, but materials don't just...well, materialize. I make my own stuff but I had to buy the mats obviously (I even mentioned I'll probably gear the rest by leveling my gathering classes). I don't wear stuff I don't make because I want it to have my name on it. I leveled all my crafting classes in tandem specifically because I wanted to make all my own crafting tools and armor while I was leveling up. Actually the sad thing is that the economy is so screwed up right now it's probably cheaper to just buy the armor instead of making it yourself, considering that if you're freshly level 50 crafting you'll have some amount of chance of not HQing the damn things and needing to make them all over again and you'll end up spending double or more of what you would've spent.
They probably should put some kind of penalty for removing your merchandise otherwise people will do what they've been doing, just relisting all their stuff 1 gil below yours (or if they're really dumb they'll undercut you by thousands). Just yesterday I managed to buy a stack of electrum ingots and they were significantly cheaper than if I had synthed all the electrum ore I had mined earlier, so I did the smart thing of selling all my ore and buying a shitload of ingots and saved hours of my time sitting down spamming careful synthesis over and over. People seem to forget that shards cost a hell of a lot of money.
That aside, I already implied that most of my money was spent overmelding (you'd think you'd figure that out from the fact that I was talking about how painful it is) because breaking those means you lose the materia. I had my own stockpile of them but you burn through them pretty quickly. I'm not interested in spiritbonding tons and tons of trash level 30 armor myself just so I can fail at overmelding 30+ times, it's a lot more efficient to just buy it. Call that part lazy if you'd like, but I'd rather actually play the game.