Not price related, but may I suggest to introduce a rule all the items for sale from a member to be combined in only one single topic.
Not really a restriction as they will still list as many thing as they want.
I have seen so many times the sub forum flooded with topics from one single member. Check the BST to see what I mean.
You must create opportunity to equally display all members who BST at any moment.
Personally I find it much easier to work out if there's something I want if the items are listed separately. Just my opinion.