I think it's worth it if you do a lot of your own maintenance and your car is currently tired out and in need of refurbishment. You more than make up for the $50 in auto-x entry fees on your first purchase from Mazdaspeed Motorsports Development (MMD). Plus, for your $50 you get to auto-x twice! If you've never autocrossed your Miata you're truly missing out. With MMD you purchase parts at/near dealer cost. This can be up to 40% or greater discount on oem parts. Plus, you don't have to deal with your dealer which is a plus if your local dealer is crap. I live near Finishline Performance @ Rosenthal Mazda and they have okay pricing on web orders (but horrible prices for walk up customers). If I need something right away and Finishline has it in stock I'll pay a little bit more and get it from them since I can pick up locally. But most often MMD is cheaper than just about anywhere else even when you factor in shipping charges.