Right, but they probably get close to zero from the self-hosted WordPress users. The revenue is from people paying WordPress.com to host their sites. That's the number of users that's relevant, and it's a much smaller number. The self-hosted users that are the majority don't count for much.
On the self-hosted side they probably make a reasonable amount on premium licensing for WooCommerce addons in the WooCommerce marketplace as well as JetPack & Akismet.