The decision is usually argued on price and decided on something else, which is why so many self hosted bases end up abandoned two versions behind. Three conditions predict success here, and a company that meets none of them should rent instead however good the arithmetic looks on the first page of the spreadsheet.
Condition one: the content cannot leave
Sometimes the answer is genuinely that a contract, a regulator or a customer commitment says this content stays on infrastructure you control. That is a real constraint and it settles the question immediately. If the constraint is a preference rather than a commitment, it is worth writing down which one it is before building on it.
Condition two: somebody already runs services
A platform or infrastructure team that will adopt the base as one more service, with the same monitoring and the same patch cadence as everything else, makes this straightforward. A favor from a willing engineer does not, because favors end when the engineer changes team and the base is then nobody's.
Condition three: you will run it close to stock
Every local change is a thing to re-apply at the next upgrade. Companies that stay current with self hosted software are the ones that decided early to accept the product's opinions and spend their effort on the articles. The ones that customized are the ones running an old version with a known issue nobody has time to address.
What it costs even when it works
A host, backups with a restore that has actually been tested, a patch cycle, and whatever search service the product expects you to supply. None is large on its own and together they are a standing claim on somebody's week, which is the number that belongs in the comparison against a subscription.
Questions people ask about self hosted knowledge base
Is a hosted version of the same open source product a middle path?
It is usually the best one: the vendor runs it, you keep the export and the option to bring it in house later. The price sits below the closed competitors and above zero, which is the honest number either way.
What is the most common failure?
An upgrade deferred because it is painful, then deferred again, then a security advisory that applies to the version you are on. The base is rarely what breaks; the calendar is.
Does self hosting help with a public customer base?
It adds exposure rather than removing it. A public surface on your own infrastructure is a public surface you now patch, and the content is the least sensitive part of the system by definition.
How do we keep the option open?
Insist on a clean export before you write anything substantial, and check it again after a major upgrade. Portability is a property you verify, not a property a license gives you.