does not mean that some won't attempt to - even feel further incentivised to do so.

Sure, and in raising up their posts they will make them more visible to potential downvoters. That's the purpose behind the curve. With some further evidence we might want to refine the parameters a bit but the fundamental idea is sound.

An author with a small payout might, in cases where the post is marginal, actually be better off leaving well enough alone and taking the smaller payout with less visibility.

Anyway, it doesn't really matter what happens in one particular case or another. What matters is that which becomes systemic, and my point about mathematical impossibility is that it isn't impossible for low-payouts to systemically escape the curve by buying votes. Some might, but only by volunteering to stand out from the crowd and be scrutinized.