I've done quite a bit of analysis on this in the past. It's amusing that despite you saying that groups or hiring don't work for you you'll still get people telling you to do just that. Of course, they're right in that in may well be cheaper, but it doesn't just come down to money for some people.
All my numbers are in GBP, excluding VAT and are based on the south east of the UK. For a 40,000 plane flying 100 hours a year, with a generous amount for maintenance but no engine fund, I calculated the cost at 136 per hour (i.e. 13,600 per year), including the cost of funds for the inital purchase. To get down to 110 (approximate cost of renting) you need to do 150 hours a year.
For people that just fly for the hell of it, 100 hours in a year is quite a few. For a more typical 50 the cost is over 200 per hour. This is why groups, where they exist, can work well - 4 pilots doing 50 hours each gets the price down to less than 100 per hour, which compares with a typical 1/4 share which costs 10,000, plus 100 quid a month and 60 per hour. Actually this would be slightly cheaper (90/month) but probably would result in periodic extra expenses for maintenance which the ownership figures already included.
I suspect people will say my figures are on the high side, but I've based it on an expensive airfield, insuring an inexperienced pilot and tried to include enough for maintenance to give a worst case scenario. If you end up spending less that's great. Also people will tell you to fly permit aircraft, microlights, paragliders and whatever else, but only you can make that choice.