The problem isn't hosting, it's the maintenance and plumbing.
Companies learn the same lessons painfully when it comes to build-vs-buy. There is no such thing as "buy". There is "build", and there is "buy-and-build". Purchasing and deploying (or in executive speak, "implementing") a particular solution is at best 30% of the work - and less than that of the cost. The remainder goes into integrations, maintenance, customisations, ongoing configuration, adapting to ongoing user behaviour changes, adapting to ongoing development needs, etc.
Running an IdP is one of the very few ventures where four nines of reliability is still inadequate. Once you have a centralised auth, it CAN NOT break.
Companies learn the same lessons painfully when it comes to build-vs-buy. There is no such thing as "buy". There is "build", and there is "buy-and-build". Purchasing and deploying (or in executive speak, "implementing") a particular solution is at best 30% of the work - and less than that of the cost. The remainder goes into integrations, maintenance, customisations, ongoing configuration, adapting to ongoing user behaviour changes, adapting to ongoing development needs, etc.
Running an IdP is one of the very few ventures where four nines of reliability is still inadequate. Once you have a centralised auth, it CAN NOT break.