Once again - there is no fundamental reason why fitting the A with the refuelling probe should be expensive, since the hardware and the great majority of the clearance work can be ported directly from the B and C. (The B's up-and-away characteristics will not be much different from the A because the aerodynamic differences are small.)
It certainly should cost less than boom tankers. On the other hand, the US may well put a vast price tag on the conversion, or assign it to the Block 12 configuration, while suggesting brightly that the partners might want to junk all those Froggy Airbus things and buy some shiny new KC-46As. Coalition interoperability, don't you know.
After all, it's not as if JSFs will be flyable at all in an operation that the US doesn't support, or that they will necessarily be flyable after the owner sends regrets to an invitation from Washington to join it in a war.