BMX drive trains are not any more expensive than any other area. If you look at sugino 75's, Race Face, etc. they are well over $200. The thing is, you get what you pay for.
I run a chrome set of profiles with a titanium spindle and bolts with magnesium pedals on my 29er. They will never, EVER break. (Plus I got them second hand dirt cheap) way cheaper than I could have gotten a nice set of single speed travativ cranks.