The hosted-or-not decision is usually argued on price and it rarely turns on price. What you are buying is a set of jobs you would otherwise do, and two jobs that nobody sells at all.
What the subscription actually covers
Hosting and uptime, search that works without configuration, permissions, an editor people will use, and updates you do not have to apply. For a company without an infrastructure team those are worth real money, and self-hosting means owning all five.
What it does not cover, at any price
Whether an article is true, and who is responsible for it. No hosted product asks anybody either question by default, which is why hosted bases go stale at exactly the same rate as self-hosted ones: the subscription bought the infrastructure problem, and staleness was never an infrastructure problem.
When self-hosting is genuinely cheaper
When you already run infrastructure, when the data cannot leave your network, or when your base is small and static. Below a hundred articles with a few editors, a self-hosted open-source base is a very small amount of work.
When it is not
When the person who set it up is the only person who can update it. A self-hosted base with a bus factor of one is the most expensive option in this list, and the cost lands at the worst possible moment.
The question to ask either way
Who gets an email when an article is due a review. If the answer is nobody, hosted and self-hosted are the same product with different bills, and the entire decision you have just spent a month on will not affect the outcome you actually care about by a single article.
Questions people ask about knowledge base saas
Is open source a real option here?
Yes, and there are several mature ones. The tradeoff is the five jobs above rather than the software, and the honest comparison is the hours, not the licence.
What about hosting it in our existing wiki?
Usually the best answer for internal bases. The wiki is already paid for and already used, and what it lacks is the review record rather than the pages.
Does hosted mean our data is stuck?
Only if the export is poor. Ask for a real export during the trial and check it contains the hierarchy and the attachments, not just the text.