What payment platform to use so I don’t lose money?

I’m only charging processing fees for my vendors right now: 2.9% + .30, a problem is that the marketplace doesn’t charge the commission on shipping. So on a $10.41 purchase ($5 item + $5 shipping + sales tax), the vendor is paying .44 to me but PayPal is charging .60.
Then on top of that I have to pay .25 to send the vendor their part of the money. So all together I’m collecting .44 but paying .85.