Did you know those thick bags need to be reused like 50 times just to break even with the thin ones on energy use? Most of mine just sit in the trunk, so the whole thing feels like a tax on forgetting your bags instead of a real fix.

My dad built frames for years out of scrap 2x4s and a couple of bolts, and the trick was he never glued the joints, he just drilled them so the uprights could be shimmed with a folded business card when they started to slip. A $12 pine frame beats an $85 "starter" kit any day because the wood is thick and the hardware is simple, nothing to strip out. Once you go that route you can also size it to whatever you're binding instead of squeezing a big book onto a frame built for a small one. The pre-made ones cut corners on the exact part that matters, which is the part holding the signatures steady while you sew.