I've seen pugsleys for around $1200 on ebay, but I assume at this time of year they will get bid up toward or past $1500 by budding snow bikers.
Here's one starting in that range right now:
http://cgi.ebay.com/SURLY-PUGSLEY-Si...d=p3286.c0.m14
If you're set on <$1k, you pretty much have to luck into a used one. New frame + 2 large marge wheels + 2 endomorphs + 100mm BB brings you past $1k already even if you already have another bike to strip for remaining parts.