firstly, I'm assuming you didn't build it but are asking for advice in buying it, if you did build it, then don't read the next part which is just me being brutally honest (I do that a lot)
whatever the market or buyer will pay... for me, it's a modified frame which can't be un-hard tailed, and an okay motor which may or may not be burnt to a crisp from the open pipes, so I'd pay scrap value, but it depends on the buyer