I'm not entirely convinced that the seller was trying to rip anyone off initially. The buyer seemed very rude in communication with the seller and a lot of people will try to "punish" bad behaviour even when it hurts them too. Especially when there is a strong emotional response.

In this situation both the buyer and the seller feel wronged/victimised and that makes it difficult to get a rational/equitable resolution.

Whatever the outcome I bet both parties will still feel hard done by and learn to be more bitter rather than learning how to reduce the risk of something similar happening in future