i got mine $750 last yr... sold it liao... luckily got a 12-24 at a much cheaper price after i miss my wide angle lens...
prices has gone up for almost all lenses... too bad just have to bite the bullet nowadays...
i dunno why ppl are always concern with sharpness for wide angle... most of the time u shoot at f8 thereabouts anyway...
the 10-20 is more than capable, 10mm is a big difference...
get the 12-24 is only if u can live with the 2mm short, else its a better lens not becos of sharpness, but more for color, flare and contrast which is superb...
my old sigma is very good, but i have to do some tweaking to get my results, the 12-24, the contrast and color is way better, but doesn't mean the results is better, just need less tweaking thats all...
anyway just buy the sigma if budget constraint....
post it in BnS, u never noe...someone might just sell u....