The subject of the sentence here is not really "users." It's the entire concept of "more users." The users aren't doing the "equaling." For this reason, "equals" is correct. You could think of an implied gerund being the true subject:
(Having) more users equals more profit.
Edit: This is not my contribution, the credit goes to Tᴚoɯɐuo, but it's important enough to add that only some verbs really work with this construction. Verbs that, as Tᴚoɯɐuo said, "go better with existential facts and their consequences or demands. equals, means, leads to, results in, brings, takes, gives, asks for, demands, etc. A stretch in solitary and no TV gives a man plenty of time to think."