Are you asking for your own business?
Or to compare for your region?
As @MsM said, larger barns generally include a schedule of charges in the boarding contract.
Generally a smaller operation may charge for blanketing. But that would mean putting on & taking off, once. Not multiple changes at HO’s whim.
Feeding supplements might require owner prepack to lessen workload for feeders.
Vet or shoer visits need to be scheduled when the owner can be available to hold their animal(s).
Especially for the vet, unless for routine vax when the whole barn is scheduled with same vet.
For injury, emergency, why would owner not be available?
Note: most boarding contracts include agreement to have Mgmt contact vet for emergencies.
If barn workers are available for routine services I’d expect a small charge - ~$10/horse.
Longeing falls under Training, IMO, same charge as for a Training Ride.
Medical treatment - administering meds, bandage care or more should be HO’s responsibility.
When I worked FT & had a horse that needed 2X daily bandaging, I paid a barnworker to do the AM, then drove 1h each way to do the PM, 7/D/W.
Paid cash weekly directly to worker.
”‹”‹”‹”‹”‹”‹”‹Meds were packaged to be fed with grain ration - no add’l charge from BO.