The referees are assigned before the season starts. Many of the top referees have a primary conference like the Big 12, but once they get their schedule from their primary conference, they fill in games with other conferences. The Power 5 conferences pay a referee as much as $2,500 - $3,000 per game but they pay expenses out of that. Others pay less than that but pay expenses separately. Some NCAA referees make it their full-time job.
Ironically, they don't get paid as much for the NCAA tournament games but its an honor to be selected for those games (I think they pick 100 referees for the tournament). In 2013 they were paid $1,200/game for the first weekend, $1,400/game for the second weekend, and $2000/game for the Final Four weekend plus expenses. It's probably more now. It's not unusual for a top referee to call 4-5 nights/week but most of the ones I know didn't call nearly that much because they had other jobs.
They've all worked their way up the ranks from high school games. In fact, a lot of really good high school refs have jobs that don't allow them to travel so they don't call NCAA games. I've called games with referees who are doctors, lawyers, judges, etc. My friend that got me involved in Houston refereeing was a senior VP at a major oil company.
Referees go thru lots of training. Continually. I can remember going to refereeing clinics during the summers and paying money for the right to call AAU games. You would be assigned 2-3 games/day and they have very experienced referees evaluating the officials at every game. You get pulled aside afterwards and they critique your calls. It included things like how clearly you report a violation to the scorers table, or your position on the court, or communication with the coaches. I've spent 15-30 minutes getting critiqued after a game a lot of time, maybe called 6-8 games and paid several hundred dollars to attend a clinic. It was almost a requirement that if you wanted to call varsity games, you had to attend an off-season clinic.
Anyway back to the Big 12 refs for the KU game. They don't usually assign "crews" but we might get one of the referees from the ISU game on Saturday, and 2 different ones. There are only about 1000 NCAA referees and the Power 5 conferences like the Big 12 take the cream of the crop from that group.
It was mentioned that they only called 12 fouls on each team on Saturday. 24 fouls is low and some of those were to put a shooter on the line at the end of the game. I would say 35 fouls is a pretty good average. Believe me, the Big 12 supervisor of officials know how many fouls each referee usually calls and what the coaches think of them.
