Do you mean simple buying and reselling or do you mean intentionally trying to buy up enough to reduce the supply and drive up prices?
Neither are all that great for a sustained price increase; when you buy up the cards you are still buying them so even if the price does go up, you profits only will if you can buy enough to significantly reduce the supply. In fact it requires a pretty odd situation for this to work without revealing those involved to be bad at economics or are basically gambling via e-bay or vast conspiracy so that enough of the supply will be impacted for the inflated prices to stick.
Though it may sound sarcastic, those first two are actually quite plausible. >.>