2. You can still be locked into a single-supplier when you pay for third-party FOSS support. In fact, most third-party FOSS support comes from a single supplier.
3. FOSS that doesn't have a sustainable business model attached to it rarely serves the needs of enterprises. There's FOSS alternatives to Sharepoint, but what's your FOSS alternative to Tableau? Salesforce? Slack? Will you actually save money by using it, compared to just paying a vendor?
From a purely technical POV, I'm pretty sure that feasible alternatives exist to all of these, e.g. I don't think Tableau's data viz product does anything that couldn't also be done with relative ease in R. Of course, these commercial offerings extend way beyond the purely technical domain where FLOSS makes the most sense; but that has little to do with "sustainable business models" - R itself is plenty sustainable on its own - and a lot to do with extremely niche or obscure "needs of enterprises" that FLOSS projects are either not clearly aware of, or not very interested in supplying. Niche and obscure problem domains have always been problematic for the open source model, this is nothing new.
It's zingers like this that keep me coming back to threads like this one! "No wireless. Less space than a nomad. Lame."