Some cards being sold I would definitely suspect botters. On the other hand, not everybody that one may suspect is a botter actually is.

For example, because I'm at the point where all I need are the rarer cards, I spend lot of time trying to get them, mainly with a lot of frustration with the occasional 'At Last' or 'Wow, that was lucky.' And in hunting the rarer cards, sometimes you duplicate and put them up for sale. Botting would destroy the accomplishment for me of obtaining a rare card, or for that matter, any card.
And I'll just reiterate what I've said before and a general agreement with Zid on botters. They are bad for the game because what they sell competes with what people sell who do not bot. And because they spent no time or effort in obtaining these botted items, it's basically gaining something for doing nothing.