Hi Rich,
Between V3.12 and V3.13, Photo customers got minor improvements, but the Standard customers got these plus three additional airports, two of which were major international airports (these ones were already in the Photo version). This is why the Standard upgrade was charged but the Photo one was free.
The full Standard product is cheaper than Photo, as it has fewer airports in it.
Over time, we are working to bring everything up to the same standard and coverage.
Regards,
Iain M.