I think $199 would only make sense (to me) if it came with full vehicle insurance, which IMO is something they should be able to do with FSD. Personally, I am thrilled I did not spend $10k up front. And based on resale values, FSD is worth at best a couple thousand dollars.
If FSD was transferrable to another Tesla, even with a small fee (under $500), I probably would have purchased it. I am betting a lot of others would have, too. I can't fathom why Tesla does not get this, as I think it would vastly increase FSD purchases.
Once FSD is ready, I would really like to have a limited free preview, for say 24 hours or X miles. Also, ideally it would be nice to rent by the day, so when I need to do a long road trip, I could rent it for that purpose.