Earlier quoted context omitted.
Do you know for sure that Mullvad sells DNS data? They claim to not log anything, including DNS.
I don't believe Mullvad sells DNS data, largely in part to their much higher pricing model when compared to Nord/Express/et. al Their FAQ confirms this, assuming you trust them. https://mullvad.net/en/help/no-logging-data-policy/#no-logs
If a provider can sell a VPN for $1/month as a loss leader and make $5/user after selling all data, what keeps a $10/month VPN from making >$15 doing the exact same thing?