So he's being evasive and hostile. While there have been some court cases affirming the right to resell software, it has generally only been in the form of individual licenses. Volume licenses will generally have a clause in the contract to the effect of how it can only be used for systems owned and used by this particular organization. Microsoft, Adobe, and anyone else you can name basically doesn't want someone paying say $10K for an unlimited user license, then turning around and selling copies of their software for $10/seat when Microsoft might sell Windows for $150/seat.
So while the software might pass activation scans, and all that, it would still technically be pirated because A) the company did not have the right to resell this software if it is a "bulk" license, and so B) this guy does not have the right to resell the software because of A.
The price of the unit as a computer isn't unreasonable, but when you factor in the software... That is where you'd get into trouble. I'd be quite interested to see what a Microsoft or Adobe official would have to say about this. If I had any contacts within either company, I'd see what I could arrange, but alas I do not. My guess would be that they would take issue with this guy's statement, and very shortly after the guy's auctions would mysteriously disappear from eBay.
The choice is up to you ultimately, but this just does not seem on the up and up to me.