CS3 -- antique value?

Perhaps the buyer is counting on people not to realize they do not get an upgrade discount from Adobe for this old version, and so they are duped into thinking they made a good deal towards purchasing CC.

There are a lot of people who don't want to go to the Cloud. And there is a lot of layout work that doesn't require anything more than CS3. And the bugs are known, & there are probably fewer of them. In other words, it could be a legitimate notion of how to make some money, as well as an illegitimate one.

That's a possibility... I wonder if he's shipping these copies out to other countries?

I was using CS3 only until recently.

Another reason some folks use old software is they are using old computers which can't run newer software.

Sometimes they're using old computers for financial reasons, and sometimes because there's a particular application they depend on which has been discontinued and won't run on modern systems.

The absolutely most stable platform I ever used was Windows NT. I'd use it & watch my wife's Mac crash & crash, but NT just kept plugging along. I'd use it today if the software would work & if it would take the needed memory with all the new stuff. Sadly, Microsoft never got one as stable again...

> watch my wife's Mac crash & crash

The early Macs did that a lot, I often got daily crashes. It got much better with OS-X (10). I'll have applications freeze occasionally (mostly Adobe stuff) but rarely have system crashes.