Interesting.....that's probably written into the bylaws of the chapters to make sure that those chapters who take an active role in coordinating/hosting events will receive some monetary benefits.
FWIW, if the NJ chapter is as good as the National Capital chapter, the fee should be well worth it. WE had a great time. Very well ran.
Here are some pics of my wife participating in a BMWCCA hosted HPDC last year.