Currently on the Marketplace when a bid is received, there is no way to enter into a negotiation.
There should be an option as a land owner to submit a counter proposal to a bid.
In this way you can at least acknowledge to the bidder that the bid was received but is too low. The process should be automated, and allow as many rounds as necessary.
There should also be a ‘Not interested in selling’ option you can set for land to prevent any bids from being entered.
Bidder submits 3k bid for a property you as the owner would take 7k for.
Owner submits counteroffer for 7k
Buyer adds funds to his wallet and accepts the counter offer.
Property/Mana is swapped
I think this change alone would do a lot to speed up the sales rate in the Marketplace.