If the superchargers have been rebuilt and ceramic washers replaced then it's a pretty good deal!! If you decide to pass on it can you forward your friend's info...??? lol
If you need to do complete rebuilds on both superchargers it starts to drive up the price....if you take them in and get a shop to do both may be in the range of $1,000-1,500...but if you take them out yourself and send them out to be done would probably be between $700-900!!
The other major factor is if they were properly maintained and serviced because 150 hours is getting up there especially if they weren't taken care of..!!
The price is right,,,
You do want to see if they have the ceramic washers or not. If so, replace them NOW. I have seen many places charge 300 dollars to do the rebuilds.