Just off the top of my head....
I would think only pages that reflect poorly on you are worth deleting completely.
Assuming the information on the page still has potential value to someone, why wouldn't you just semi-orphan the page (way, way, way down the navigation path) so that it draws off very little link juice, but still has
- the potential to bring a visitor in by search
- the potential to stand as a "related pages" link to keep people on the site longer.
Or if just make it a pure orphan so it doesn't take a drop of value from the site, but is still there in case there is an undiscovered link out there somewhere (possibly somewhere on your site that will not automatically disappear when you remove the original content).
>>It's not any different from a store dropping products
I think it is. There is a real cost to a store keeping a product in the catalog and there's even a real cost to a library keeping a book on the shelf. For online content though, it's more "catalog" or "index" space (to use the library analogy) that's precious rather than "shelf space" which is essentially infinite.
So really you're curating your catalog more than your shelf space.
>>both a cost of creation and a cost of removal
A cost of removal might be that you have inadvertently created a broken link somewhere else on the site. So if I remove the item from the "catalog", but not the "shelf", it's effectively removed as far as new users are concerned, but at a lower cost in that I don't have to pull a database dump and make sure I've nailed every occurrence of links to those pages.