Generally, flying for fun is an affair of the heart not of accounts and cost-benefit-analysis.
That being said there was a good article in the last-but-one Popular Flying from a guy with a Jodel who had kept a very detailed record of his expenses over about 3 years.
Group ownership is an excellent way to go in my opinion, for affordability & often keeping the thing flying a decent number of hours a year. Also variety. I think I'd rather have shares in 3 different types of plane than own a single one.