Tracking days skiing has nothing to do with the cost for me. I just like comparing year to year how I'm doing and try to set personal goals (mainly with skiing more vertical every year).
I don't track days for any other activities as there are no other activities that I do on such a consistent basis like I do skiing.
I'm kind of like above. I'm not into a lot of personal ski stats except for days per season and total number of ski areas visited lifetime (about 90). For over 50 years I have kept track of ski days in my head during the season, but then forget as summer rolls along, except to know that my all time highs were 45 in 1976 and 50 in 2015. In between for about 15 years when my 4 kids were young I was lucky to get 10 days a season, didn't have a season pass anywhere, and it was easy to keep track of days.
For me and a lot of skiers the number of ski days per season is a very strong indicator of "how serious" the person is about skiing/boarding. It may not be a foolproof measure of skill, but when someone tells me they ski 20, 30, or 50+ ski days per winter it's clear they have a big commitment to the sport like myself, and not a casual participant.
I kind of cringe at the "how many days have you skied this season" threads because I've never lived less than about 90 mins from a ski area, so it's hard for me to rack up big numbers. I hope that's going to change soon. In the past a high percent of my ski days were full days since I drove 2-3 hrs to get to the place I was skiing.
I'm impressed with Dr Jeff's consistently high number of ski days per season, esp. since he is a family man too. That's double commitment
I do a fair amount of biking in offseason, don't track total bike miles, just how long I'm riding on a specific day, although sometimes I ride for a period of time like an hour out and an hour back. I ride a slow hybrid bike mainly for exercise and fresh air. I also bike commuted about 50% of the time to work each summer since 2006.