Yes, Tumblr users are allowed to charge for their blogs and content, though there are specific tools and community guidelines to follow. [1, 2, 3]
You can monetize your blog using the following built-in tools and methods: [1, 2, 3]
Post+ Subscriptions: Tumblr has a built-in feature that allows creators to lock specific posts behind a monthly paywall ($3.99, $5.99, or $9.99/month).
Tip Jars: Users can set up a virtual tip jar to receive one-off monetary support directly from their followers. [1, 2, 3]
Important Things to Keep in Mind:
Copyrighted Material: You cannot charge for fanfiction, fan art, or works that use intellectual property (IP) you do not own. Tumblr’s policy strictly prohibits profiting off copyright-infringing material.
Tumblr's Cut: If you use the native Post+ subscription feature, Tumblr takes a 5% cut of your subscription earnings. [1, 2, 3, 4]
So I got my answer. And while you can monetize your posts, what that tumblr blogger was doing was against policy. I was technically correct.
