Conor McGregor’s $40 million year notwithstanding, few fighters get rich in mixed martial arts, even when they compete at the highest level of the sport.

For fighters on the low end of the sport, working their way up the ladder, it’s almost impossible to make a living without holding at least a part-time job. Every dollar counts.

And that knowledge is what makes John Castaneda’s actions following his Aug. 11 TKO of Angel Cruz on a Combate Americas show in Los Angeles all the more remarkable.

Cruz’s original opponent fell out, and Combate officials were scrambling to find a replacement for him in a bantamweight fight. It was looking bleak for Cruz when Campbell McLaren, the head of Combate Americas, reached out to Castaneda.

Castaneda had little reason to take the fight. A split decision victory he scored over Gabriel Solorio on April 25 had earned him a shot at the Combate bantamweight title. Taking a fight with Cruz would put that title shot at risk.

Castaneda, who trains in Minnesota under Greg Nelson at the same gym at which former UFC champions Brock Lesnar and Sean Sherk trained, agreed to take the fight.

“I took the fight because I am training full-time, six days a week, regardless of whether I have a fight coming up or not,” Castaneda said. “A couple of months prior, I was assuming I was on that card because I was asked to be on it initially. Then things fell through and I realized I wouldn’t be on the card. But I knew there were a lot of 135- and 145-pound fights on that card and something like this could happen. So it seemed right to take it.”

There are a lot of similarities between the UFC and Combate Americas, including fighters stepping up to take bouts on short notice. And in large part, that’s due to McLaren, who was one of the UFC’s earliest employees and the Combate Americas’ creator.

Like the UFC, McLaren gives post-fight bonuses, but he does so with a twist. He doesn’t give out Fight of the Night and Performance of the Night bonuses. Instead, he awards his fighters a finish bonus.

Any fighter on the card who wins by knockout or submission earns a finish bonus of $2,000. It’s McLaren’s way of encouraging action.

“I’m biased, but I think this is a better way because it encourages all of them to try to have the Fight of the Night,” he said.

Castaneda has fully bought into that line of thinking. He said he will go for a finish regardless of whether or not a bonus is at stake.

Though he was training at the time he accepted the bout with Cruz with just five days left before the fight, his diet wasn’t as clean as it normally is. And Castaneda said it left him feeling “sluggish” in the cage.

He won the first round, but was hardly dominant. McLaren said Castaneda “was taking a bit of a beating.”

It was a different man who went out in the second round. Castaneda, chastised by his corner, went hard after Cruz. He took him down and unloaded a vicious ground-and-pound, forcing referee Mike Beltran to stop the fight.

Awaiting the post-fight ring announcement, Castaneda sidled over to McLaren. He’d had a pre-fight chat with Cruz, who thanked him for taking the fight. He’d learned a little about Cruz’s family.

He saw the difficult situation Cruz was in, fighting because he needed the money.

And so, McLaren said, Castaneda leaned in and whispered to him, “Give Cruz my bonus.”

It was a remarkable act of selflessness because Castaneda himself isn’t getting rich by fighting and he moonlights as a trainer at Lifetime Fitness to help supplement his income.

Castaneda almost sounded embarrassed when asked about it. McLaren said he became emotional.

“It really choked me up,” he said. “I’d never encountered anything like that. MMA is a very charitable sport and you see fighters starting GoFund Me pages to help each other a lot. But this was a little different situation and it was so impressive. This came in the heat of the battle after a very tough fight.”

Castaneda, who graduated from Minnesota State in Mankato, Minn., with a double major and degrees in criminal law and Spanish and interviewed for a government job as a Spanish analytic linguist, said giving the bonus to Cruz was the right thing to do.

“After the weigh-in, he stopped me and thanked me for taking the fight, and he said if I hadn’t taken it, the fight probably wouldn’t have happened,” Castaneda said. “He told me without the fight, ‘I couldn’t feed my family.’ That really hit home to me. This is real. This is life. He’s doing this because he has to in order to support his family.

“I met his kids, two little girls, and they were so cute. This was an extra fight for me and I wasn’t expecting this money. And so when I got the finish, I told Campbell that I could do without it and to give it to [Cruz].”

It’s not often anything like that happens, but it’s one of the many things that makes MMA unique among sports.