myXXX.app is not the most sought after domain type. Maybe you'll be able to find a customer for $100-$500 by outbound.
But looking at how many decent myXXX.app are available, I wouldn't count on it:
are all available at reg fee.
If I was looking for this type of domain, I would focus on domain sets where both XXX.app and XXXapp.com
For example yourpoker.app and yourpokerapp.com, or getpoker.app and getpokerapp.com