Apart from that, SSO is just a handy feature that non-Enterprise customers usually don't need while Enterprise customers do, so it's ideal for differentiating customers. That said an Enterprise edition contains much more than SSO in many cases, e.g. audit logging, containerized deployments, extensive support, etc.. That's what you pay for with an Enterprise offering, the SSO feature is just a small part of that.
This isn’t true, IMO, most people just don’t realize there’s an alternative to one user account per service. We’ve convinced non-enterprise users to use an objectively bad solution of password managers because every SaaS service hides their SSO option behind enterprise pricing.