Whirly
You've picked up a good point, the # of planes one is operating. It is clear to me that the cheapest way to run planes is to own a number of identical/similar types, be a licensed engineer and do your own servicing, buy replacements in decent quantities. Let's say you need a panel resprayed; you do all 10 at the same time and it will cost hardly more than doing just one.
Those people who have made money renting out planes (30 year old cans usually, so bad you wouldn't fly it if you owned it) to flying schools have tended to be in that category - I've met a few.
Taking this to a closed group, the planes can be on a Private CofA and if somebody is able to do the maintenance then the operating costs drops quite a bit. This would be a pretty cost effective way to run a club. The 5% min share is a non issue if you run more than one.
But I don't agree about fewer operators simply being worse. The number of operators needs to match the demand. I know of an airfield where there are around 6-8 fixed wing operations. The # of customers is perhaps enough for just one. So all of them are permanently verging on going under. (Incidentally you can imagine the politics there - the rumour mill from that place occassionally surfaces even here
) At least 1 operation goes bust there every year, some in a particularly messy way, but in GA there's always somebody else who wants to have a go.
Taking this to the UK as a whole, this is a large factor in our decrepit GA scene. There's always somebody who wants to play around in this (at the supply end, or the customer end) but those at the supply end are usually doing it without any business sense, and those at the receiving end tend to be skint anyway. Now, if those operations at that field were replaced with just one, properly managed and equipped, it would be an extremely successful operation, easily running a dozen £150k planes and doing so at prices no higher than the cheapest UK spam can rate.
Englishal
A CofA is some £600. At 500hrs/year, that works out to 40 pence per airborne hour. The name of the game is utilisation, utilisation and utilisation
The other things all help of course but without utilisation, it's all a waste of time.