Uganda does offer one of the lowest priced gorilla permits at 600 USD as opposed to Rwanda’s permit that goes for 1500 USD.
The Uganda Wildlife Authority sells 96 gorilla permits per day for both Bwindi National Park and Mgahinga National Park combined (88 permits for Bwindi and 8 permits for Mgahinga). Due to the high demand in the peak seasons, booking a permit at least three months in advance is advised.