If you have the patience, ebay stalking can help.  I follow certain items on my feed and every so often you get a Buy It Now at a reasonable price.  I scored Astonishing X-Men (last year) and SA X-Men Vol 1 (a few months ago) that way for under a hundred bucks each.  I do have to say that I was mighty lucky and that these auctions are rare.  You pretty much have to catch them within a few hours of being listed.

Otherwise, as rustbelt mentioned, scouring comic shops would be another option.