While I understand the classic Walmart grease pot is defunct, KMart still has theirs for about $5.

You can get a EN13537-rated 20*F down bag, the Kelty Cosmic Down, for well under $100 if you shop around. Heavier, of course, than Western Mountaineering, but definitely lighter and longer-lasting than a comparably priced synthetic bag.

For shelter, moving up from the blue tarp, and a lot lighter, is the 8' x 10' silnylon tarp from Campmor.com (actually Equinox) for $80, 14 oz. Add mason's twine for guylines, aluminum gutter nails or homemade stakes from coat hanger wire, a chunk of polycro (the shrink-to-fit storm window material) for a ground sheet and a couple of sticks (found at the campsite) the appropriate length for poles, and you have a first-class shelter under a pound for about $90. For bug protection, pick up some wedding-veil material from JoAnn's Fabrics and drape it from the roof of the tarp. Moving the other direction, you can use clear plastic for a tarp which will last a few nights; just be sure to pack the remains home with you if it shreds.

For food, no reason to buy those spendy tastless freeze-dried backpacking meals--you can put together your own from supermarket ingredients. Check Sarbar's website for details and lots of recipes, most of which require only boiling water (no dishes to wash!).