That is not a real economy. That is true. Real economies have taxes, wages, overheads, etc. However items are devalued because they have lost their value. It sounds redundant, I know, but understand demand is down and supply is up. To get people to buy goods that they may not need, you need to lower the price if you want to sell anything.

I bought Titan's Heart for 9k. That is a ridiculously low price. However I did not need it, and still do not. If the price was the 50k like others I just wouldn't buy it. I bet that seller is happy they got some money for that. I bet other sellers are not. Those unhappy sellers wouldn't have gotten my money anyway. They can get another person's money, but if they can't maybe they should lower their prices as well.

If there were no vendors in this game, crafting would be more important than the main story itself. Never has that happened in a final fantasy game.