According to this link [1] 200k would put someone above the 80th percentile and not far below the 95th percentile in terms of household income for the DC metro area, so I don't see how that could be considered "underpaid", especially when you consider the benefits.
The type of person who gets elected to Congress is likely to be far above average in charisma/intelligence/skill, and hence underpaid relative to what they could attain in the private sector
rendang|2 months ago