What is more expensive for your organization: time or money? In general, your options that cost less take more time to setup, and vice versa.

It seems like cheap is more important, so I would roughly do:

• SSG like Hugo or MkDocs
• store the content in S3
• serve with a CDN like Fastly or CloudFront
• authentication via VCL or a Lambda using OAuth

It’s such an insane amount of money