Studiotools B2B review for Climate Click

Since I didn't got an answer from support since 9 days - and there are no other contact options I try my luck here... I would love to active the "Merchant paying" option for all our orders... but it seems to be a bit a blanc cheque. Can you tell me how to calculate / estimate the costs in advance? Our average order value is EUR 5'000 (starting at EUR 500 and up to EUR 50'000). Is it a % of order value? Or how can I calculate in advance what I will pay / offset? Many thanks, Reto PS: I will be happy to change the stars, if I get an answer