I'm thinking a broken engine is worth only the price of the accessories.

If a piston is cracked or ring lands broken, from obvious high boost or lean out, you don't know what damage it done to the bores, valves or valve seats, or the already fragile CA crank or rods.Without ultrasonic testing, you surely can't guarantee it.

As a whole, you are selling a parts engine. Just like a parts car who's floors have rusted out.

At $400 ex-turbo, that's getting closer to the mark. People are silly to use a second hand 'unknown' turbo on any big rebuild, with new turbo prices being what they are now.