There are no transfer fees when sending IOTAs, that doesn’t mean you can’t ask for fees for certain services built in or on IOTA
Many of the next big IOTA things will be services for you which you will pay or NOT (self regulated economy).
– Having tasks performed using Qubic on top of IOTA will generate revenue for the people making the computing power etc available for Quorum computations.
– Permanodes will generate revenue since asking to check on a transaction from x years ago will be a service for which you can charge etc. Especially in an IoT environment with millions or billions of Tx per day, you will need big drives to store the data of 1-x years.
– Many of the ecosystem applications built on top of IOTA (check ecosystem on IOTA homepage) will involve fees, monetary incentives, big computation etc.
– In general, the core protocol is for free (sending data and IOTAs, or even using Qubic in theory I believe (if somebody just decides not to charge you for instance)) but if you want to use services that are based on the resources of other members, you will simply pay what the economy wants at tat point.
– There are definitley a myriad of for profit things possible on top of IOTA!