"High level" is the problem. It's a subjective number. You're going in wrong direction. Make it an objectively low number, maybe average full time salary in their state with potential to hit performance bonuses based on a number of measurable things that help their constituents.

Their pay needs to be linked to their performance in office and yes, a separate matter, but there needs to be tight regulation (and oversight with enforcement) for monitoring their wealth before, during and for a period after serving in office.