I would say the average is $10-15K per year. It also heavily depends on where you are based... 1Ks out of IAH spends more than 1Ks out of the coasts. EWR may be the exception. Do not forget GUM based 1Ks who probably bleeds money out of their noses to fly on UA.
1Ks based outside of the USA will naturally have higher spend as well.
As for differentiaing between those who flies on higer fares and those who flies on lower fares, this is why the upgrade hierarchy is based on fare paid. I know those who flies Y/B/M fares almost never miss an upgrade, even on last minute tickets. I have a friend in IAH who buys his tickets for work only 1-3 days in advance and never misses getting an upgrade. He is a GS though.