If SE won't shadow ban RMT bots, let us do it ourselves. Let us block chat messages based on content, such as "Cheapest", "Buy", "xxxgold.com", etc.
To set one up, just highlight the offending text, right click it. and select BLOCK, and you never see a message with that text again.
The blacklist is useless for this because the spambots change their names so often.