That makes sense, Like for Like would be a much lower differential.
At the end of the day the Charter operator has to make a margin, if you dont make a profit then you dont stay in business for long. Any operator will know that you first have to pay for the aircraft (DOC), maybe that price includes the insurance, maybe not, that depends on who owns it and whether the owner insures it or it is insured through the operators insurance scheme. You then need to put fuel in it and pay a pilot to fly it.
JetRanger costs per flying hour: Say £300/£350 inc insurance for the hire/owner. Fuel (depends where you buy it) lets say for the sake of argument £90.00 per hour. Pilot, allow £60.00 (maybe a Day Rate will be applied subject to the task being undertaken). Allow for AOC charges and admin say £50.00 per hour. You are up to £500/550 per hour for the charter and that is before the operator puts a profit margin into the equation. Thus most JetRanger operators will be quoting based on between £550 & £650 per hour.
If you took the above and the figure quoted of £130.00 per hour for the fixed wing then at the top of the priricing band you are about 5 times more expensive. You then have to consider the versatility offered by the Helicopter, very often Point to Point and if not then generally at least a lot closer than the airfield required by the fixed wing. In general I do not think you can fairly draw a comparison between the two forms of flying.
The above is really just irrelevant number crunching. What it actually comes down to is that Helicopters are a lot more expensive to Maintain, Insure and Operate.
Well thats my thoughts anyway.
