Locally, I can buy the following air filters for my '08 Liberty:
$11 Fram
$16.29 Purolator
$21-$24 Champ, NAPA, Wix
$51 K&N
I know the sales pitch / differences for the K&N, but my thoughts on the others is that they are pretty close to the same thing.
Ignoring K&N and prices for the moment...