Two times I tried to buy a used laptop from individual sellers. I accepted the asking price and each time the sale went thru with a delivery date. Both timess, after receiving no shipping confirmation by the promised date I contacted the sellers. The first seller responded "I sold it to someone else." The second seller never responded but continued to list the same laptop at a higher price. I complained to Amazon which canceled the orders.
I wasn't out of money but it spent several frustrating weeks waiting for the laptops I thought I had bought. On ebay if seller fails to honor a winning bid there is an opportunity to leave negative feedback. Welching on a winning bid is a serious matter in the ebay community.
Not so on Amazon. There is no way to leave feedback unless a delivery is actually made. Neither seller I ordered from seemed to have the slightest sense of moral or legal obligation to fulfil a completed sale and both continued to fish around for a higher price. There is no remedy for this failure under Amazon's feedback procedures.
I will no longer buy from individuals on Amazon Marketplace. Don't try it unless you have a lot of time and patience.