I think it is safe to say that there are other costs beyond just the plastisol, colorant, bag, label, flake (plus salt in some cases) etc. Paypal or cc processing fees is another "hidden" but substantial cost.
It is hard to put a number to some of the costs but I think you must add them in with at least an arbitrary number you assign or a set % to the cost for these other expenses.
Otherwise, your "profit" is suspect and you are doing fuzzy math like the government does.... LOL!!!
Jim