I don't know what patches are selling for now but a number of years ago as I recall, they were selling for about $2 per hundred. That makes them about 2 cents apiece.Patches are so inexpensive, I've found it hard to justify the time and effort to "make my own"...
I bought a yard of blue/white striped pillow ticking for about $6.
That yard of pillow ticking was 36" long by over 48" wide. That's 36 X 48 = 1728 square inches.
Since my patches are about 1 1/4" square. Dividing 1728 by 1.25 I get 1382 so even with some waste, I'm getting over 1300 patches out of that yard of material.
$6 divided by 1300 = .005 or, 1/2 cent each. At that rate, instead of 100 patches costing $2, 100 patches now cost me 50 cents.
Yes, the difference isn't much but these little things add up.