On Mastodon you don’t need to pay for your verification links, just make sure the sites you link to have a reciprocal backlink with rel=“me” included, as described in the Mastodon doc.
Some platforms, e.g. GitHub and my Hugo sites using the Blowfish theme, even recognize Mastodon profile links and will augment them automatically.
I had to augment the backlink manually in my JSON-generated resume.
<a href="https://universeodon.com/@technicat" rel="me">technicat</a>
Just remember to resave your profile after making the change to trigger the verification check.