As Kirk says (and does not need to apologize for, IMO), that’s a common record-contract arrangement, but by no means universal. Of course some artists release their own records in the first place, so the margin on their own direct sales is much higher . Others have a contract with a label that allows them a certain quantity of discs for sale. Others don’t sell their studio albums, but do sell concert recordings–sometimes even CDRs burned on site, so you can go home with a disc of the very show you just saw.
The point of the thread was how things have changed from the first heyday of rock. There are more models in play now, and at least in some of them musicians are definitely making more live than on record.