This is not a price war
When someone has misplaced something important to them, they may put it on the market with a financial incentive for whoever can find it. It’s a totally legal action to do.
What it isn’t, however, is an opportunity for others to come along and start a bidding war for a phone that isn’t theirs! We just hope that if someone came upon Caroline’s iPhone, they had the good sense to ignore the white notice and do the right thing.