Just Jane on the circuit?
Pure speculation, the principal purpose of getting JJ airborne is as a memorial to their brother. Money raised from taxy runs has been toward that aim and mutual support with the museum.
Unlike PA374 , JJ is the major exhibit at the museum. Any tour away from base would have a negative effect on the museum. In comparison with the Vulcan, fuel costs will be minimal at 200 gal per hour, but then of course slower transit speeds would n reflected in cost per mile.