I do not understand why one would carry both a ground cloth and a bivy. I've never used a bivy, but having both seems superfluous. Also, I see lots of GG polycryo ground cloths on gear lists, those are ~1 oz and I'm sure Mika could find something similar to use. If he prefers a bivy, it seems to be quite easy to make a 6 oz one with silnylon, momentum and nanoseeum (SMD Metor style) for $30-40. Plus, Mika would be considering solo tarps which, using a silnylon MLD Grace as a reference, would weigh less than ten ounces (7.5 for the spinn one which, while pricier, is much less than the tents you mentioned).
So, taking into consideration a 10 oz tarp with either a 1 oz ground cloth or a 6 oz bivy, I'm looking at a 13-18 (10.5-15.5 for Spin, 8.5-13.5 for Cuben), oz shelter package with stakes and guys, doubling or more the weight difference that you come up with and coming in at $140 for MYOG bivy w/ siltarp or even 260 if you'd like to buy an MLD Superlight bivy for $155 which would be the same as the MYOG. If you go the MYOG route, even a Cuben Grace tarp will come in under $300 for the complete package and weigh 13.5 ounces with stakes.
I am sorry to be so critical of your post and I'm sure that you came from a place of wanting to help. I'm sure you come from a different place than I do on tarp camping and I respect your experience and viewpoint. I'm trying to make the point that there are ways to make tarp camping both lighter and cheaper. Personally, my setup weighs 6 ounces total with stakes and cost me $165. I use a Zpacks Hexamid Solo with a plastic groundsheet and a dual-use mosquito headnet that I suspend from my shelter to cover my face while sleeping. There are certainly many ways to camp and I hope Mika finds one suited to his hiking style.
Sorry to be so serious and long! :-)