For the last 24h, we had few people buying normal priced mats only to resell them at 2000% without taking the risk to loose money in the process.
A solution to this would be to have deposit cost, that are lost if the item is not sold. The deposit cost is given back if the item is sold; then a sell tax applies.
Without any deposit cost, only stupidly high price will be seen on item for sell, breaking the economy.