The idea of flying an R44 at half the commercial rate sounds very attractive.
So with 44s renting out for £400 to £450/hr that means you will be getting to fly for £200 - £225/hr
Let's just do a quick back of the envelope calculation on that on say a Raven II.
Taking RHC published figures you will need to allow for overhaul costs on a time flown or calendar basis this will be $177,826 or around £118,551 or approx £54 per hour flown and if you dont't fly at least 183.33 hours per year it will still cost you £823 per month.
Dependant on the experience of your group members and the value of the machine you use expect insurance to cost £600 - £800 per month
Then there is hangarage. Depending on where you base the machine don't expect to pay less than £400 per month + 20% VAT.
Maintenance will set you back £4,000 - £5,000 per year if you are putting on an average of 4 hours per week flying.
And finally there is fuel. The Raven II is the easiest helicopter to calculate required fuel for a trip, it burns a litre a minute or approx £105's worth of Avgas an hour.
Adding that up on the basis of 183 hours per year you get an hourly equivalent rate of;
£54 overhaul allowance
£49 insurance
£22 maintenance
£30 hangarage
£105 Avgas
£260 total per hour
OK it's only a rough guide, not chapter & verse,
It doesn't cover the unexpected things going wrong or RHC hitting you with a SB to replace the fuel tanks by end of 2014 at a cost of around at least £9,000 unless the helicopter you buy is a late model which already has the bladder tanks.
To be on the safe side add another 10% to your hourly rates to cover contingencies and divi then it up at Christmas if all goes well.
Although I have used RHC figures in some of the above I have also used 10 years experience of owning and flying an R44.