They don’t extract anything. You agree to perform a statement of work for an agreed to amount of money. You set the price of your labor by agreeing to take the job. If the business (which risked its capital) makes money, they get to keep that. If they lose money you still get your paycheck. Sounds like the guy taking the most risk gets the biggest reward. So would you be ok returning some of your pay if the company you worked for had a bad year and lost money? Didn’t think so. Here’s a challenge for you. Start a business and show us all how it’s done correctly.