I'm not aware of any mail providers that require DNSSEC. Were you thinking of DKIM? That's just 1 more TXT record (to publish the public key used to verify the signature), and some mail signing software if your mail server doesn't have that feature built-in (which is freely available).
...Or are they, except not in cash? :) Jokes aside, that's a fair observation, but then one should be able to "transfer" their address by paying a one-time fee, rather than getting a GSuite subscription.