There aren't many mobile apps you can buy from Apple. Apple is primarily a hardware manufacturer. Their entire product lineup consists of devices[1].
https://www.apple.com/services/ https://www.apple.com/logic-pro/ https://www.apple.com/final-cut-pro/
Of course, these are not the bread and butter products.
I find it a bit pointless to separate their hardware and software. I know few people who run Windows or Linux on their Apple hardware. For me, Apple is primarily a products company that excels in fusing hardware and software together. They are increasingly expanding into services, too.
And similarly again there's none you can buy from Oppo and Samsung (I'll consider the Samsung store negligible in terms of market share).