Yes it is worth the $50. You will get less air restriction over stock filter, and you don't have to change it, just check it with every oil change, and if its dirty, wash it, and put it back in. I had it on my previous car and never had to worry about new filter. Here is the filter cleaning kit: http://www.knfilters.com/clningacc.htm
You can purchase it at Pep Boys.
I know you don't have to change your air filter every 3 months, but to give you an example here is my story. I really with i purchased K&N for my Jeep before this happened. I went off-roading and while crossing water/mud, i got some of it inside my air box. But i didn't know this until Sunday when i decided to open it up. About 3/4 of the filter is filled with light brown color mud. Now, if i had K&N i would just take it out and wash it, but now i have to get a new one instead, and most likely its going to be K&N filter.