Pay Pal fees and Membership or Pay to Blog Plugin?

Hi... guidance please...

I am considering the Membership or Pay to Blog plugins...

PayPal's fees for sellers are
1.9% to 2.9% + $0.30 USD
to get paid.

If I collect a listing fee of 20 cents per transaction I still owe PayPal 30 cents + per transaction.
How do companies who use your software charge a 20 cent listing fee if they lose $ per transaction? Are they holding off on charging fees until the end of the month to count as only 1 transaction? If so, can Membership or Pay to blog do this.. automate fee collection at month end based on total posts for the month, and not upfront?

Suggestions appreciated! Thanks!