Rich in the state of Oregon, defined as the top one-fifth annual family incomes, starts at $109,000.
For Connecticut, the top fifth starts at $144,000 per year.
For Washington DC, at $157,000 per year.
Source: Baker, Lisa, "Measuring Wealth," BRAINSTORMNW Magazine (June 2008). I have a call into the magazine asking for sources.
While these numbers don't include an explicit comparison of cost of living, I believe it is implicit in the numbers.