I bought a used P-80 for the DV8R we are using for flight control system research. It too is worth quite a bit more than the engine. Yes, you can get burned on a used engine, but in general, Enrique's arguments don't make sense. You can get a "lemon" right off the shelf just as easily as a used engine. The benefit of a used engine, as long as its been reasonably treated, is that the "infant mortailty" is already past and as likely as not, the engine will go fine for quite some time - this is especially true of the P-80's and P-120's which are over-built for their thrust ratings...