For you to compare Brock with a guy on the bottom of the undercard is absurd. Every promotion in the world does the same thing with a high-profile/high-potential new fighter (roger gracie in sengoku recently, gardner in pride, etc...). Heck Couture was a headliner in his 2nd show against Belfort. Or look at the NFL. They don't give the #1 pick and the 7th round guy the same money because they are both "0-0". The bottom line is you get what you can earn.
But these guys are not the issue here. Brock and guys who CAN demand a salary are fine (like in all orgs, all sports, and all career fields). The problem is one that should be dealt with by putting in a "minimum salary" like other sports. Or even a scaled minimum like the NFL that goes up according to how many years you've been around.
I agree with you the lower guys should be paid more, but saying Brock is "entry level" just like an undercard fighter is ridiculous.