Per se means 'by itself' or 'in itself', and is used when you are talking about the qualities of one thing considered on its own, rather than in connection with other things.
It is not the money per se that makes them unhappy, but the single-minded pursuit of that money.
There is no indication that just having a degree per se improves your chance of getting a job.
Synonyms: in itself, essentially, as such, in essence