Depends what kind of music it is really... If he's doing mostly background tracks then it's a lot simpler and faster to make than any LP worth listening to. (with years of training obviously)
He's probably reusing some of the same structures/progressions/samples/beats from track to track which also cuts production time massively. If he's good at improv he can noodle a half assed melody over chords and it'll sound great for a backing track. I doubt he bothers recording a real drum kit every time too but who knows.
Still excellent value for money if his tracks are good. I doubt this is his only source of income.
Source: I've done similar things