I think this is overly complimentary to big business and what's essentially predatory pricing.
The reality is you can't just carve out on feature and say "we pay for this." I mean that's true of a lot of things. The big revenue generators pay for a lot of things, but how things are billed is important. Remember, not to long ago people paid for Netscape, but now its laughable to pay for a browser. Its arbitrary to have this 'buffet' mentality and seems purposely shaming towards people who rightfully complain about ridiculous pricing structures like this.
I'm also skeptical that SSO costs vendors money. Maintaining and supporting an authentication database is a huge expense. For every SSO client, its one less Adobe or whatever account that needs to be hosted. Less helpdesk tickets about password resets, etc. SSO tends to be once and done. Hosting millions of accounts and being the sign-on provider for them is not 'once and done.'
Lastly, a lot of orgs don't do this. A lot arent SOC2. That means they'll just use whatever account the vendor supplies, and most likely without MFA, but their SSO would have provided that, thus making everyone more vulnerable. This is a great example of how exec salaries and stock buybacks and other things have priority over security because security is seen as a cost-center and without litigation or law, stuff like this becomes the norm. Oh and now there's one more source of passwords out there and another potential hack.
This is just greed and predatory. Its not the wonderful largess of big companies. It fact, its quite the opposite.