I think the conversation is not so much about tarps as about dirtbagging it to achieve our bag nights. I was a dirtbagger par excellence in the old days when my backpack was my old USAF duffel bag loaded with all my stuff and thrown over a shoulder---and using a combination of very cheap sleeping bags in tandem for 0F temps instead of paying $400 for a quality down bag.
Going cheap works for those in poverty who want to live outdoors---and blue poly tarps aka walmart tarps work great in many applications. My first several tipis were made from these kind of tarps.
Ultimately though I have found high quality gear (and very expensive gear) to be cheaper than repeat buying of inferior ineffectual products. I think Skurka calls it "stupid cheap" or something. Give me a high quality $700 WM sleeping bag and it will outlast a half dozen lower rated bags and still be going strong after 20 years and will take me from 50F down to -20F with no problem. I like having one piece of gear that does it all, and find it comical when guys have 4 different sleeping bags for the 4 seasons.
The Arcteryx rain jacket is a perfect example. 10 years ago I wasted $200 on a Marmot Minima gtx rain jacket with paclite gtx which developed pinholes in the first 2 years. I just wasted $200. Had I purchased the Arcteryx Alpha SV right off I wouldn't have had to resort to substandard rain shells like the Marmot or ponchos or anoraks or all the rest. So really dirtbagging is the art of wasting small amounts of money for substandard gear when tested over the long haul and when tested in real world hellish conditions, like 80 hour horizontal 60mph rainstorms or a series of blizzards at -10F. High quality always wins out in the end.