The cost for a vendor processing CCs is something like (iirc) 3% of purchase price + $0.10. The benefit to vendor of selling you credits (aside from the fact th

The cost for a vendor processing CCs is something like (iirc) 3% of purchase price + $0.10. The benefit to vendor of selling you credits (aside from the fact that you might not use them all), is that they only have to pay the $0.10 portion of the fee once for every, say, $20 worth of washes instead of paying the flat part of the fee every single wash.