Some thoughts (which may or may not be half baked, as my knowledge and experience with SP is limited)...
* Isn't storage of documents inside of Sql Server more expensive than on disk?
With 4 TB disk drives expected to dip under $200 once the Thai plants are fully back, space is usually a non-issue.
* Isn't document sharing about the least $$$ profitable reason to implement SharePoint? How does that provide a return on investment?
In my experience, document sharing itself does not. It is when you also implement workflows and use reconciliation of concurrent edits that SP starts showing its strengths.
* Since Search can now catalog files on disk, and with full text searching, why bother "cataloging" manually by providing tags and the like?
You can indeed use automated indexing. That, however, assumes that all users adhere to a strict discipline and all documents have mandatory headers that contain all information needed for indexing.
* Some reasons you might want to bring docs into SP might be SOX, HIPAA and other secure access issues.
* SP requires an expensive person to configure and maintain, so you need some $$$ impetus ore a need to satisfy a requirement.
True. However, your SP admin will likely double as a TFS admin, because TFS is just a specialized SP, so the skills are transferable.
* The best stuff is only in Enterprise, (ie: PerformancePoint dashboards), and that costs a lot more, so you need to be sure you can't service your strat[e]gic decision maker(s) any other way just as well. SSRS can provide report subscriptions, for example.
If you look only on IT operations (including development), TFS provides much better management reports.
* If indeed, SP is the future, *which I think it is*, since it is web based, then it is useless to resist the Borg. But like the Cloud, when must you surrender? Maybe not for three years.
* Organizational tools are wasted on people with no knack for creating effective teams to begin with.
I have been using both TFS and SP for several years. Personally, I prefer TFS and I asked for better document handling in TFS, which would make SP redundant.