RE: RC hobby Market SLUMP?
It might be that what your selling is pretty large and there are a limited amount of buyers for a plane that size. I've heard others with giant planes say the same thing lately. I sold two engines on RCU and they went pretty fast. I never bought anything so I can't say anything there.
Also it's hard to fault people for waiting for a higher price, that's human nature. Doing that in excess is not fair but it's reality.