Another place that gives a break for age 60-69 is Lost Trail Powder Mountain, ID. Season passes are currently $450 for adults, $375 for 60-69 and $150 for 70 and over. That seems like a lot for a place that is only open Thurs-Sun unless a holiday week. When I went there on the last day in February in 2015, full-price adult day ticket was $40 full-price and it was $32 if you were 60-69. Not sure what daily rates were for 2015-16 or will be next year, but it skis bigger than you may think and Thursdays and Fridays have a good chance of finding untracked.
Hmm, I have a friend in Missoula. Maybe next time I'm headed to Big Sky I'll think about a little ski safari in Idaho. My ski buddy I drive with the most will be 65 soon. I think that is useful for a few places in ID and MT.