If just for main L&R, I'll change my estimate from at least 50% to at least 75% that will fall in the 0-$5000 bracket.
I have some idea of teh speakers in peoples signatures as well as the questions/suggestions that get made here. There are guys who I know have main speakers over $10,000 but that is very rare. Generally the Salk Soundscapes are the top end of this forum and more commonly, the Phil3's.
I'm not saying that I'm certain no other, more expensive speakers, are better, only that you start paying a lot for a little better.
I think the break down would be more biased towards more expensive speakers on one of the less scientific/practical forums. I mean if people there are willing to pay $5000 for cables, they should be happy to pay a good bit more for speakers.