I look forward to your open letter to underquilts and top quilts. Sticker shock is pretty common for noobs.
I, too, suffered from major sticker shock at all the things I couldn't afford. I tried using tent tarps and blue Wally World tarps. It was all a colossal waste of money, and I got wet. As many have said, save your coin for a proper tarp rather than putz around with "not exactly."
I didn't listen to the advice on this forum, and I paid dearly for "not exactly." You can get an HH Hex tarp for $70 and get years of enjoyment out of it, or you could go for "not exactly." Don't waste your time, if you ask me.
Wanna buy a crappy 12x12 Guide Gear tarp, 2012 edition? It hasn't kept me dry, but maybe you'll have better luck.