The shareholders would pay for Musk's pay package by having their shares diluted. It's not as if Tesla has to provide any money for that, so it's not really comparable to giving employees a raise.
Employees can (and most often are) paid in those company shares as well, so no difference.
Employers (and employees) generally have a pretty good idea what the market price is for a particular job. If they have to fill 100 positions and offering $25/hour causes them to get 100 qualified applicants who accept the position, they could offer $35/hour, but this is like saying that the employees could accept $15/hour when another employer is offering $25. Some explanation is required for why they would.