There will never be a 150M gate.
The Super Bowl held in Dallas, Texas which had 100,000+ people in attendance had an expected gate of $170M taking into account gate, both ticket window and resale. Now I cannot find the comparable numbers for the largest attended gate in a combat sport, or the UEFA Champions league final but I would venture to say its below for the Combat sport or near the same for the UEFA Champion's league final(at least regarding per ticket price per seat)
That's an established premier league, in a very strong business region of the nation, that is the most watched TV production in the United States (which can field a 22 person lineup that can buy out the UFC roster salaries 10x over.) isn't going to be outdone by just about any other professional league on the globe let alone the UFC.
As for how much this would cost to make it so in your example to reach the 150M by itself:
First off there is no 120,000 person stadium. The largest stadium in Brazil according to wikipedia is Estadio do Maracana which seats 80,000, the largest in Canada is Olympic stadium with 67,000 seats. Now of course you will have people sitting on the pitch but going back to the Dallas example, for the NBA All-Star Game they had a record 108,000 people for the NBA all-star game. The normal NFL capacity of the stadium is listed at 80,000. and that's with a stadium that is multilevel and built to be cross use. So assuming a best case scenario they are going to match that in Brazil and that makes the average ticket price $1400 no matter where you sit.
Going back to the Super Bowl comparison, seats started off in the nosebleeds for that amount. Which just isn't realistic. Mayweather-Cotto by comparison had $1500 upper bound ticket prices. And that was in a smaller arena, so whatever comping effects there was, were offset by the number of tickets available.
Merchandising has no comparable in the UFC to my knowledge that would match the NFLs for a single event.
Sponsorship and PPV sales, I already responded to with how unlikely it would be to reach this target and make it a viable option for the UFC.
Simply put if I was Dunder Mifflen, or PWC, or whomever Zuffa has advising them regarding compensation I would tell them under no circumstances agree to this demand.