How large of a tank are you setting up? Up to $80 to replace a cartridge is insane! I use the Fluval 404 and haven't bought any new replacement media yet.
The only media I replace every two weeks is poly-fill and the bag I bought sometime back in Late March / Early April is still more than 50% full.
75g Planted Barbs Denison, BlackRuby, Tiger, Albino Tiger, Green Tiger, Cherry, Gold, Checkered, Odessa.
NonBarbs Cardinal, Neon, RummyNose, Bloodfin Tetras, Z. Danios. 1RTS. Amano, Bamboo, Ghost & RCS. 20g Long Shrimp Tank RCS, Tiger, Amano.