While I can't attest to the specific value of this engine,(about $40-$50) Balsa Kits of RC AND Control Line, are in HOT demand on Ebay. Were talking actual balsa kits and not ARF's. Engines in NIB or, very good condition are still VERY hotly contested there. For example, a Top Flite AT-6 Texan balsa kit,(one of which I own) recently went for just under $400!!
Some guy had 4 Moki 61 long strokes,(of which I own 2), all NIB, and all sold for well over $200 each. Nobody wants the ARF's, they all want the kits.