1. community editions may be free and will get you started but once you get beyond a certain point you will want the commercial editions which are definitely NOT free.
This is not true of most OSS software. However if you get over your head you can hire professionals to help. (Just like the commercial software world!)
2. If you need support then this is NOT free. In fact "professional services" can be very expensive.
This is true of all software commercial or OSS. Or medical or legal services.
3. If your open source choice is not something you would or could contribute something to then what is the benefit. I couldn't contribute to MySQL or PostGres code. I might add something to Hibernate or Solr at a push.
You don't have to contribute code, you just use the software. Buck Woody uses many OSS packages as well as MS software, I doubt that he contributes code to all of them.
I use Linux, Python, pandas, postgresql, SQLite as well as Windows, VS. PS, C# and SQL Server. I haven't had to contribute any $$$ or code to OSS, but I have helped clear up documentation and offered feedback on features. And unlike Microsoft, many of the authors have responded to me and made positive changes.
4. Open source projects seem to attract the masses. It used to be that only the big players could afford an MPP appliance and only they had "big data". Now that many people say they have "big data" projects such as Hadoop start to come to the fore.
Oh! Those dirty "masses".
The masses don't give a !&@! about open or commercial software. Or "big data". But if I need to spin up a bunch of servers twice a year to crunch some demographics data, do you think I'm going to use Windows or OSS software on the cloud?
5. Open source projects with some overriding governance seem to be the ones that survive. The rest fragments and die.
This is true of commercial software too. I have lists of commercial software that I loved that is dead due to mergers, changes in leadership, corporate whims, etc...
At least with OSS, I can take the source and fork it, keeping the product alive.
6. Very few people can afford to work for free. Businesses chasing free software from companies without a viable business plan are going to be left holding an ugly baby.
Most OSS is written by developers for and by corporations. Even Microsoft does OSS development. I can get a job right now writing OSS and make the same or better money.
Please try better arguments next time...