Vendor prices are WAY too low. Currently, you have two options: vendor it for next to nothing (most items < 10 gil) or put it up on the market board. If vendors offered a reasonable price for items, then I think a lot of the undercutting casuals would vendor items rather than deal with the hassle of the market. For example, a housing item is up on the market for generally ~50k. The vendor price is 100 gil. This is too much of a gap and doesn't reflect the rarity of the item. So the people who need money put it up for a fraction of the market price to move it quick. But, what if the vendor price was 5k? I think a lot of people might just vendor rather than deal with the market board and also to have the money in hand. You combine this with the limited space to sell and it puts a lot of pressure for people to make quick sales.