In the overheated market, there are surcharges on conservatively determined valuation results, which are too high for the financing banks, then they also say "njet" even to otherwise good customers. The seller will have heard offers in the bidding competition that have raised his hopes. Now he will want to test how high he can go without a bank of one of the bidders putting a wrench in the unity of the parties involved. Even if the price ultimately lands close to your last offer, he will accept another one of similar height, but not yours. You are the one who has poked into his price dream bubble with your offer. That you only went 10k above an estimated value of 330k was unwise: in an overheated market, to speculate on such a small delta between "value" and "market price" was indeed more audacious than just bold. In my opinion, you should now write off the deal, file it away, bury it. Gladly also ceremoniously: burn the printout of the exposé and then there is a candlelight dinner, dress up, pop open a good bottle. Laugh about the rookie mistake and don’t go on the next hunt like amateurs again. Existing properties are a field of their own, and in my opinion should only be considered as an alternative to new construction with a lot of experience. Therefore: better keep looking for plots of land – not the next existing property right now.