App B charges the restaurant less.
The restaurant considers a cheaper menu price on B.
Lower B’s menu price.
Leave A’s price unchanged.
The discount can stay on the lower-fee app.
Lower A’s menu price too, although A still charges its higher commission.
The discount on B also reduces receipts on A.
Keeping A’s original price instead risks losing its membership benefits.
The restaurant could also keep both prices unchanged and retain B’s fee saving. This illustrates an incentive, not a prediction of restaurant behavior.