Ronda Rousey -- Must Win UFC 184 ... So I Can Afford Mayweather Tickets!

UFC pain machine Ronda Rousey says she has EXTRA motivation to beat the living crap out of her opponent at UFC 184 this weekend ... she needs the prize money to pay for tickets to Mayweather vs. Pacquaio!!

The baddest woman in the history of MMA was training her ass off in L.A. yesterday ... while the DJ pumped salsa music through the gym ... and looked extra ferocious as she gears up for Cat Zingano.

But when we asked about a rivalry between boxing and MMA ... Ronda called BS -- saying ALL combat fighters have a respect for each other ... and that's why she's pumped for the big fight in May.