The $629/year is if they use a certificate from one particular company (Digicert) that manages keys in a way that would be easiest for them to fit into their cu

The $629/year is if they use a certificate from one particular company (Digicert) that manages keys in a way that would be easiest for them to fit into their current workflow. There are other options that would require more changes to their workflow but are much less expensive. See the responses on GitHub or the other comments here for several of them.