how is this possible?

[Rufalus]

thats no investment, thats stupidness

I think so too. You can't make a solid investment when S-E are able to change the game at will. Spending a huge amount of gil on an item with the intention of reselling it many months down the line can easily come back to bite you in the ass when conditions in the game are altered to make that item common and worthless outside of your control.