1. Fighters with the UFC are not employees. UFC is not the employer. Each fighter is in a bilateral contract agreement with the UFC. Ever see a band that is going to play the same venue multiple nights? That's probably the best analogy. One party--a company--makes an agreement with a venue. It then offers, in a separate contract, to pay a band a certain amount per performance (which can include various incentives). Nowhere is an employer-employee relationship created.
2. Point #1 has a major effect on compensation. Is is not just semantics. Employees have the protections of unemployment insurance and various state and federal laws such as ERISA. There are limits on hours worked / overtime, leave policies, mandatory payment for accrued sick and vacation time, etc. There are liability laws and principal / agent concepts that come into play in a lot of situations. On the other hand, employees are generally subject to certain employer policies regarding attendance, discipline, etc. The point is that a contractor under this type of contract is much different than an employer or employee.
3. A contract does not force a fighter to fight. U.S. contract law is very clear in that specific performance of a unique service is a disfavored remedy. In other words, if a person breaches a contract to provide a service (like a fight), he must pay the fair value of those services. If the person is so special that it's impossible to truly replace the services, the best remedy is to then enjoin (prevent) him from performing that service for anyone else until he makes things right with the aggrieved party. So if Conor refuses to fight for the UFC while still under contract, he won't be forced to fight, but he could be ordered by a judge to not fight elsewhere until he either fights with the UFC or gets the UFC to agree to contract rescission.
4. Your work situation is not like UFC fighters' positions. The comment of, "If I did x at my job like Fighter Y is doing, I'd be fired" is almost always completely inapplicable.
5. Comparing your pay structure to UFC fighter pay structure is almost always fraught with peril. When you travel for work, your work