Assuming that's what you meant? Then, you're wrong, they are supplied by Nike. Just Sport buy millions and millions of shirts from Nike, and then they distribute thousands and thousands to football clubs like....Aberdeen!
And I also understand that it isn't a bespoke kit. But this way the club makes more money from shirt sales, which is a good thing, it's not like you'll be wearing the shirt out to that trendy nightspot 'Priory', it'll get worn in the Pub at weekends and maybe the odd game of 5's, doesn't need to be fantastic quality. Would you rather look like all the scum you see wearing Celtic or Man Utd shirts everyday of the week? No, that looks 'rank and cheap'
And the more I think about it, a shirt that lasts a year then falls to bits is ideal for the club, that way you'll need to buy a new one every year, which means even MORE money for the club