You just got to keep your eyes open and look at adds here and EBay. I just won this YS 45 with pipe and header on RCU for $145. By the looks of it, the engine may never had seen full power, the header looks way long. Ive scored 4 of these engines this year and 2 are NIB and could of had more, just wasnt in the mood. This is about the going price for NIB or used with pipe.

http://www.rcuniverse.com/market/item.cfm?itemId=347570