to add to what RVM said, the Sierra pass is pretty cheap at $220 restricted and $370 unlimited. I had the triple wammy last season (Sierra/Northstar/Heavenly), but didn't ride Heavenly (too crowded, pretentious, flat spots, etc...). I loved Sierra for pow days, tree runs, and the laid back vibe and Northstar has great parks and good pow if you get there early and know where to go. If you choose to go with Northstar the local pass (restricted) is $380 and that includes Heavenly.
DAYS 15/16: 6
2010 Bataleon Goliath