I don't think their salaries high. But they have benefits of tokens. They could sell those, it's like a stock as big compainies.
People that are working with the coin dont really sell their tokens from what I noticed. Maybe they get paid on the side in Bitcoin or something because the wallets that most workers have are usually posted to the public since people wonder if the coin will receive a dump from the devs. People might not be doing that now though the question from the OP is an interesting one since the coins dont really move.