The player who announced they would buy the FTT does so paying the normal price. If a second person wishes to buy it, taking it away from someone who just bought it, they do so at cost +1 DP. The cost would continue to increase by 1 for each subsequent “steal” in that round.
One notable exception is that Pixies will buy the FTT at whatever the current price is minus 2. No one else benefits from their discount.