Used 360 Value?
Rules about buying/selling
Buyer always have multiples of the thing you offer to them, so it's need to be cheap.
As a buyer from those same people the item you want is ALWAYS the last one they have available, thus expensive.
Econ101 Supply/demand curve. Even though it may be fantasy.
I wouldn't give 500 for what is there unless it was a solid provable runner. Intake and MT's are worth a couple hundred, the engine is a core 200-300. X-heads meh... good for the resto crowd only or folks stuck in the early 2000's and prior.