Except profit margin has nothing to do with stock price, its Net Profit / Revenue Cost. It is purely a representation of the return of the business, with no factors of how the market values the operations. The raw amount of profit is irrelevant. The actual operation itself returns 3.5%. You're thinking of other ratios that include the stock price.
The product the employees provide is their service, and because their service isn't unique or clearly that valuable, the profits are what they are. If the employees provided a greater product (service) that produced greater economic output/profits, then they would be entitled to higher wages.