I agree Rabbit. Most builders start motors at the HP level for $18K-$19K. I would expect to get a used motor for that price. I know what I have my motor in the classifieds for. It's a season old and I don't think I would take $15K for it.
Then again, if you didn't go shaft rockers, went chain and not belt, standard lifters and didn't opt for a big name head and intake package, you probably could get close to $15K but stretch to get to the 1000hp number.
I am curious to see the invoice and what went into this motor.