For starters, it really, really, really upsets the Apple haters. Which is good for a laugh to see the mental gymnastics they go through to spin this news or make it irrelevant.
Apples share price is high because they have consistently high revenues/sales. This benefits me as an iPhone (for example) user.
High sales means Apple has reason to keep pushing the envelope with each new iPhone. Like consistently coming up with the worlds most advanced custom processor. It provides them with money for R&D for future products. High iPhone sales means there’s an excellent choice of aftermarket accessories (companies aren’t going to tool up to make products for phones that sell a fraction of the iPhone). High iPhone sales are what drives developers to iOS, providing us with a superior App ecosystem.
There’s a few obvious ones, for starters.