For some of those services it might not be profitable with there cheapest plans.
There certainly is price gauging from some vendors, but it's not unreasonable to charge a premium.
Supporting a narrow particular set of vendors (Azure OIDC and Okta, OIDC/SAML2) is dirt cheap. LDAP is another story and a real enterprise from support standpoint. Every time it's a support case with a high chance to allocate an engineer to solve the issue. I bet most of listed services don't support LDAP.
BTW. I have no issues with the pricing policy. You ask price others are ready to pay.
Also it could be an opportunity to eval other products with SSO from the box.