Turns out you are right. Not only are the scent cartridges proprietary, they also contain the batteries, meaning even the batteries are proprietary! $20 for 2 scent/battery cartridges. Good for 210 uses each.
Normally I get 1200 bathroom visits for 26¢ worth of electricity. 1200 visits using the proprietary battery cartridges costs about $57! About 220 times more. Oh, oh, I’ve saved sooo much money on electricity 
