What you will notice is the difference in the value of the names to the owners and what buyers are willing to pay.
If they sit on the names they will eventually get their asking price but their asking price may well increase too in time.
However, having said that, buyers are willing to pay a bit more now than before for 4 letter combinations similar to yours. $40-$50 seems to be the current going rate to resellers. You might get more from serious collectors. If you wait, the value will increase dramatically.