What should I pay for used Paxton Novi 2000

[wht88cpe]

A friend of a friend is apparently removing his existing engine with Paxton Novi 2000 supercharger- He's going with a big block. It's on the car and running at the moment. But it's not in this local area so I can't take a look at it- as if I would know the in's and out's of these anyway. Looks like $3500 or so new. So assuming it's all there and nice condition what should I expect to pay ... 40% 50% 60% ?

Thanks ahead for any input.