Because there is a 0.35c flat fee per donation along with the 2.9% (ignored in the sample). So giving ten euros to 1 creator actually costs 10.35 to the patron

Because there is a 0.35c flat fee per donation along with the 2.9% (ignored in the sample). So giving ten euros to 1 creator actually costs 10.35 to the patron. Giving 1 euros to 10 creators costs 13.50