I eyeballed one of these at the bargain barn the other night. The
"kit" appears to consist of a few yards of cheap cotton/poly fabric,
plastic bag handles, and basic directions for knitting the bag. The
bag itself appears to be two slightly tapered flat pieces, with a long
narrow piece used as the "gusset" to give the bag depth.

As the knitter you are required to cut the cloth into strips of a
specified width, then knit per directions and sew the pieces together
with the addition of sewing thread and seam tape that is not provided
in the kit.

Okso. I priced plastic bag handles ($5) and cotton/poly fabric
($2/yd). Seam tape is about $1.50, a spool of thread the same.

I do NOT know how much fabric is required for stripping into "yarn" -
I guess that's what swatches are for. You also want extra fabric to
line the bag with. I'd start with 3 yards cut into half-inch strips,
plus a yard for the lining.

$6 fabric
$5 handle
$3 thread and tape
===
$14 which was $2 less than the bargain barn was selling hte kits for.