Yes, the question is the selling price. If the passenger version costs 100M, a F version would cost less, because of the lack of refinements. So the difference in cost is the price of the creature comforts which might be 15M, 20M or 25M per plane.

Presumably the F version would have a few additions like strengthened floors and loading doors.

Conversion F’s are a red herring in this thread.

Yep, conversions are a RH.
Yep, the large doors are expensive, and the extra transfer joints around them…to continue the load that was held by the stringers where the door now is.
Not sure about the floors, certainly different panels, but pax seats and their mounts have to withstand something like 25G before breaking off, my point being the floors are pretty strong now. Floors are also the spine of a commercial airliner. Above it is just a series of rings that wobble a lot (As can be seen if you sit at the back during turbulance)
Also consider (I think it was mentioned above) that market forces play a part in the price. These do not follow a formula from the cost. If this A/c did something special, it could add extra to the price for no additional cost…so long as it stays within the band the the customers are prepared to pay.