While others argue over speculative facts....
This question is beyond broad. Yes, "they" could do any number of things. I suspect that, what you meant to ask is this: If I buy more of this item, and if the seller later determines the sale price was too low as a result of a mistake made by the seller, could I be legally made to pay a higher price. The answer to that question is no. Beyond that, without more detail, it's impossible to say much more, except that, if you find a great deal and want to take advantage of it, I can't conceive why you wouldn't do so. It's not your place to tell the seller how to conduct its business.if I ordered a few more, and they ship them to me, could they do anything after the fact?