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.
To summarise your comment, my notes in parentheses:
* This isn’t as good as SSO (I’m sure that OP knows that).
* It doesn’t meet your requirements (I trust OP to know what their requirements are, and I myself have been in situations where this would be useful).
* Implementing SSO from scratch isn’t hard. (That doesn’t mean bupkis to someone that wants to use SSO functionality of a SaaS product that they are subscribed to. Also, I’m highly skeptical of any SSO implementation that was ‘easy’ to write).
* SSO’s usefulness is limited without proper access controls within the product (…yes?)
* Only ‘enterprise’ customers want/need SSO. (This is a clear example of uninspired SaaS companies drooling over the white elephant ‘enterprise’ customer: someone with a bunch of money, that will pay for your value-add crap without batting an eyelid. I’ve worked in plenty of settings that I wouldn’t call “enterprise”, but that would’ve benefited highly from SSO. Unfortunately SSO is always locked behind AT BEST a significantly higher seat cost, but usually with a very high floor, and often behind a “contact sales” funnel. Replace “enterprise” with “business”, because that’s the reality. Then…look at your (probably B2B) SaaS product’s package differentiations, and tell me that you aren’t screwing people).
* Enterprise plans usually come with way more than just SSO (Yes! half the point is that most people don’t want this stuff! It’s mostly shovelware to make it not look so egregious to pay so much more for SSO! You’re right! SSO is a small part of that! So why force people to buy the rest of the stuff if they don’t want it? Oh, that’s right, because you’re lining up behind the other SaaS vampires to prey on basically any organisation of more than 5 people that wants have their ducks in a row).
It really just sounds like you’re trying to justify your employer’s crappy yet common sales tactics, and we’re just coming along for the ride.
That's your perspective, but let me try another one: So many SaaS products have a free/low-cost tier that allows people to get basic functionality for nothing or extremely cheaply. Users are clearly not unhappy with this and the vendor gets market share and awareness.
However, there is still a cost - and that cost ends up getting subsidised by commercial customers that have a hard need on a small number of features.
That, and the fact that even 'small' business customers these days make you fill out the same 'security review' forms that they don't understand and never read, can require a lot of hand-holding (especially if they have a procurement or legal person who wants to get their requirements in) and can take forever to do a Proof-of-Concept.
ALL of those things have costs and guess what, they end up being added to those small number of 'must have' features.
That is why a base tier might be free but suddenly you add something like SSO and the cost doubles...