Neon is making some money with fees, low and transparent ones. Don‘t know if that is going to be enough. ZAK does not need to make money, the idea is to upsell clients other services. Again, no idea if that will work. Doesn‘t work with me (I like them, however, more than Neon so far for the account itself. Neon‘s card is better though).
Transferwise is making a profit afaik.
Revolut is the odd one out. Their fees seem to be too low to be sustainable and their customer service and reliability are horrible from what I hear.