Because that wasn't the purpose of the poll. The reason the price brackets are so wide is because he wanted to see how many here would support edging the price brackets up. He said it a few pages back.
Even if that was actually his goal, the poll options are still useless.
If you actually wanted to learn something about people's willingness to accept the rise in flagship GPU prices, then you would need to cover the relevant range with sufficient granularity.
In other words you would need price points like this:
$500 ("traditional" flagship price)
$550 (GTX 980, 7970, 290X and Fury)
$600 (1080 custom and 8800)
$650 (980 Ti, 780, 280 and Fury X)
$700 (1080 FE and 780 Ti)
$830 (8800 Ultra)
$1000 (Titan, Titan Black, Titan X and 690)
$1500 (295x2)
$3000 (Titan Z)
Furthermore you would arguably have to stipulate that people should answer what they are willing to spend on a single GPU, not on their entire graphics solution like this thread does, since that skews the numbers.
Making a poll like this would actually tell you something about where people's pain limit is with regards to flagship GPU prices. You could of course also add prices below $500 if you are interested in people not going for flagship GPUs.