That was a stuff sack made with remnants of fabric used for the quilt, plus two straps I made with 12mm webbing. It was ok but the fabric is not the strongest, being made especially to be downproof.
I've since made a compression sack that does use two Linelok tensioners, it does compress the whole thing ridiculously small.
My thoughts are that such compression sack cannot be sold by a manufacturer: people would get carried away leaving expensive down bags fully compressed for weeks and months, thus degrading the fluff of the down (or Primaloft).
An attempt of destructive test by compressing to the max 1sq ft of Climashield Apex and leaving it compressed for a week, did show no degradation and I could not measure any loss in volume once left for 1hr to get back in shape. That material is incredible, no wonder it was made for the US military standards. And it's a lot cheaper than down insulation, with little weight penalty for the same level of insulation, also does not retain water.
This compression sack was made with some very strong ripstop polyester that I guess was made for Paragliders, it's not fully water-tight but well waterproof and has a very slippery coating that helps in packing the bag. It's very light too, the fabric being something like 30gsm ended up with the finished sack weighting less than 20gr.
Between the quilt and the sack, I would guess it's about 60 euros of materials; this includes the Argon67 fabric from US, 133gsm Climashield apex, Dyneema-like cord, mini cord locks, plus the LineLok tensioners and the Paraglider fabric for the sack.
The fun in making it has no price, if you add the fact of making a top-notch piece of equipment for relatively low money, it's simply awesome
What you see inside the sack, is the second quilt I've made, the green/blue one in the pics above was with 100gsm Climashield insulation; this one is made with the same outer fabrics and insulation material but it's 133gsm (4oz/sqyd) Climashield so it's a bit thicker.
The quilt is by no means "useless in spring", being about 3 thick gives excellent insulation for the low weight, and I've found it effective up to +5ºc if sleeping with a Merino baselayer and thin long johns.