$50?
AUTOHAUS.com
Autopartswharehouse.com
For my BMW I get them for 16 bucks, the Autozone price for mine is around 20. Odd yours would be higher, the BMW filter is pretty big, what car are you buying for?
In all honesty the charcoal is hardly enough to remove odors for more than an hour or two, I know, you would need 20 pounds to absorb what your car encounters during a normal month. Many times funky odors are not from the outside but rather the accumulation of moisture in the AC system that forms a moldy/fungus smell.
try turning off the AC 5 minutes before shutdown once and a while, run the fan on high, hoping to dry out the system.
Dont pay $50 for a cabin filter, go on Ebay go anywhere but dont pay $50, thats highway robbery.