I think the 3500 should be the price of the complete unit including sensor package. 

What I meant was that buying a ym2000 either head unit alone or one with a sensor package which didn't fit your combine could result in spending more to make it work then you paid for it.  I'm shooting from a poor memory here, but the impact sensor and moisture sensor are somewhere around $400 each and the elevator mount kit is maybe $800 and I'm sure the harnesses will be at least $300.   That makes nearly $2000 worth of parts other then the actual head in the cab.