--- Summit County another obvious options.
You'll have to fish out deals on lift tickets. I managed one trip to Loveland with their 4-pack tickets for $129. Total cost is somewhere around $600 even including a rental car. But that's with super cheap (post Lehman economy) air fare, car and lodging. The cost of renting a car vs taking the transport from Denver airport to Frisco is similar. But you lose out on skiing the first day not renting a car.
--- Reno is indeed a good candidate. But it's a bit trickier than SLC. None of the resorts are actually "near" Reno. Unless you rent a car, that is.
So you have to balance wanting to get in a half day skiing (Mt. Rose or Diamond peak) vs the cost of a rental car. Not having a car also limits you to the resorts that have shuttle bus to Reno.
Lodging in Reno is reasonably cheap. I'd put Reno a little bit ahead of Summit county but far behind SLC.
--- Have you looked at Whistler?
You never know if they'll run any air fare special to Vancouver, which would make it doable at your price range. Don't know any cheap lodging though.
With Denver and SLC, you have the option of skiing half day Monday, flying out around 5-6pm and getting home in the middle of night vs a redeye which get you home in thr crack of dawn. With Reno, red eye is the only way to go.