The gap starts with timing and leverage. Downey Jr. entered the MCU as a proven but damaged asset—a comeback story studios could reshape. He negotiated backend profit participation on Iron Man when nobody believed the character would carry a franchise, then locked that structure into every subsequent contract while his stock kept rising. Evans came in as a safer bet with fewer negotiating chips; Marvel offered him a massive upfront deal ($300K baseline scaling to millions per film) rather than betting on his back-end, which actually looked like generosity until you realize Downey Jr. was capturing the exponential growth while Evans was getting fixed premiums.

Contract restructuring separated them further. When Downey Jr. renegotiated after Iron Man's success, his agents played hardball knowing he was now the MCU's anchor—he went from $500K to $75M for Endgame by combining salary, bonuses, and profit participation. Evans negotiated his 9-movie commitment as a volume play (the bet being "total earnings across the slate"), but he locked in deal terms early when the MCU's true revenue potential wasn't yet visible. Downey Jr. renegotiated multiple times as each film proved more valuable; Evans mostly executed his original contract.

The business lesson is brutal: backend participation beats salary every time, but only if you negotiate it when you have leverage. Downey Jr. had the leverage of being unfireable by Endgame; Evans was still somewhat replaceable when he signed. Downey Jr. also diversified faster into production, endorsements, and post-MCU projects (Sherlock Holmes, Tropic Thunder residuals) before his Marvel income peaked, compounding wealth. Evans' net worth is genuinely impressive, but Downey Jr. essentially played the same role and extracted 3.75x more by being more ruthless about renegotiation timing.