I'm sure your restaurant is thriving. While working as a delivery driver, the restaurant owners and managers I talked to none liked the delivery apps. Some used it because they didn't have delivery otherwise but it dropped their margins to 2% or worse. Others used the delivery services because they saw a drop in orders to Skip and Uber Eats. They couldn't drop in house delivery or they would lose call in and direct orders that earned more. Now they had 3 competing delivery services and Skip and Uber out bid them for online advertising for their own restaurants.

But the next time I talk to them I'll pass on your advice. I'm certain raising prices or charging for delivery has never occurred to them.