So if you want to sell an item in this example lets say bronze dagger and you put 20gp as price when selling it, you will receive that 20gp if somebody wants to buy it for that price.

However if somebody was buying bronze dagger for lets say 10 000GP when you tried to sell your bronze dagger for 20gp seller would not get 10 000gp, instead what he put as price originally (so that 20gp). There is no question in my mind that this is at least very wierd feature if not bug.

If this is how it is supposed to work then sellers should put always super high price and slowly move down from there (which makes no sense and takes a lot of time).