Someone in the forums provided a good equation for R.T.A. vinyl (handing the customer a ready-to-apply product, no installation required on your part)
Add the Length + Width of the material, divide by two, and that is what you charge.
For instance, 3+8 is eleven, divide by two, that's $5.50. for ONE
In your job, you have 100, so you will use approximately 200 running inches of material (4 across, 25 rows at 8" = 200")
200 + 12 = 212 divide by two, you are at $106. total.
I would probably go with the rounded-up number of $1.50 each.
Sounds reasonable, right?