Peter For their "Classic" account (comparable to bunq Premium), the first 900 Euros (limit shared with cash withdrawals) every month are free and after that 2%. So bunq could probably implement this with a similar fee structure like the already existing Barzahlen integration for Germany, Austria and Italy (fixed free amount every month, after that 1.5%).
Also if bunq could make the free limits higher for SuperGreen customers, that'd maybe work and in turn also make their top-tier membership more attractive.
Of course, nobody likes paying these fees, but cash handling is a costly business.