This seems like a real knee jerk moment here. You aren’t wrong that there are predatory sellers that do exactly that, but it also seems to assume that people do not have the ability to do their own research, which tbf in a society where attention is apparently a rare commodity and heavily capitalized on, it’s not necessarily an unfair assumption. It’s just unhelpful and honestly pretty damn rude to make a blanket comment that seems to assume that people just won’t or will refuse do their research, and should just listen to your authoritative take.

Wouldn’t it be better to just rephrase your comment into something like, “Please remember to keep an eye on price histories to make sure that the displayed prices are discounted as claimed.”?

Or does it feel better to speak as if people are dumber than you are? I mean, if you need to feel smarter and better, there are other healthier avenues for that, and I would suggest that you try looking into those instead.