The "stealership" is a necessary evil, some parts are very reasonable, others really aren't.
When i needed pump parts for a 763, my local dealer wanted over 2k per rotating group PLUS tax. I don't know the exact figure, but i thought i got them from LPS for 400 each? The dealer will buy these parts direct from the manufacturer i'd think. LPS i'd suspect would buy them off a wholesaler, so one more step in the process, each step comes mark up, it's how business works. How can they justify charging more than 5 times what LPS sold them to me for?
With that said, filters are very reasonable, some times they are even cheaper than you can get them from the local truck/auto store for.
Every business needs to make money to be there when you need them, but there is an acceptable price, and one that is just robbery. I have never taken my car to a dealer for repairs, i have had to buy genuine parts before, so they still do get some money from time to time.