IMO you really need 300 hrs a year to make outright ownership viable and certainly not less than 150 hrs.
That depends very much on your priorities.
If you like to fly something nice, something which hasn't been secretly bent by somebody else, something maintained to your exacting standards, something in which any fault is fixed before the next flight, then ownership makes sense on 10 hours/year
Otherwise, yes, the figure is likely to be between 100 and 300...
If you want to fly something decent, the best way will always (except for a seriously busy pilot flying almost daily, usually on business) be a group. You can try to set one up yourself.
Just need to find several people who are willing to put some money where their mouth is - tricky! But this is no different to the situation in which the owner of a plane find himself when he wishes to rent it out. He is after renters, not shareholders, but they still need to be of a reasonable quality.