Paypal normally charges a 2.9% processing fee +.30 per transaction
So a product selling at $10 would incur a .29 fee + .30 or $.59 to you for a net of $9.41
Many want to pass this fee cost on to the customer so how do you do it.
The formula is simple - figure what you want to net out first - in this case $10 (a)
The processing fee is 2.9% (b)
The transaction cost is .30 (c)
first you need to find what I call the divider (d) = 1-b (2.9%) = .971 (d)
Now it's easy
a/d+c
$10 divided by .971 +.30 = $10.598 - rounded up to $10.60
I typically round it up to the next whole $ so I'd sell it for $11.00