How to buy a root CA certificate?

Interested in how much money is necessary to buy CA cert chaining up to a trusted root and besides money is something else necessary. globalsign advertise this: https://www.globalsign.com/en/certificate-authority-root-signing/ ===== GlobalSign’s Trusted Root Signing service allows suitably qualified organizations to capitalize on their investments in PKI or CA software to issue digital certificates which chain up to GlobalSign’s publicly trusted Root Certificate. =====