Those Kelty bags are often discounted at places like Dick's Sporting Goods, Sports Authority, etc. Worth a look, anyway. Unfortunately, down is getting scarcer and the demand is increasing….
It actually gets colder down in the valleys than on top of the mountains. Besides, don't you want to visit those beautiful high mountain lakes in Idaho? You're not in Iowa anymore! (Sorry, couldn't resist that!)
Anyway, instead of my pontificating on, which you're undoubtedly tired of, let me give you a a few references:
Start with the home page of this site that I linked to earlier. Mark Verber's website.
This survey of possible gear is downright encyclopedic, but you really just want to read the introduction to each section for general info and then skip to the end for low budget choices. There are also links to gear lists (a few don't work) and to other lowbudget ideas. No point in reading all about $700 tents, which I can't afford, either! Dirtbagging and Deal Shopping, by "Sgt. Rock"
Lots of low cost ideas for hiking, starting in your own closet, kitchen and garage. While he focuses on the Appalachian Trail, the principles are the same.
One caveat--especially with this year's drought, expect bans on campfires and probably on alcohol fueled stoves. Those options for saving money are therefore not feasible.