The scenario you describe is one of someone that owns a home in Boulder, and has owned it for a long time (likely decades).  That means the home is likely paid off (or nearly paid off), and they have a ton of home equity.  Hard to feel too sorry for anyone with 500k-1M (or whatever the number) in home equity.  

If their income is too low to pay the rising property tax, then perhaps it's time to sell the home, cash the huge check, and move somewhere further out where the average home price isn't $1M+.