Well, I was kind of envisaging more of an LAA or experimental type approach with owner assisted annuals etc. I'm not a great subscriber of the "include the re-spray ever 20 years in your hourly costs of operation" philosophy. If you don't include it for your car, don't include it for you aircraft. But, let's include the engines and the insurance like you suggested. I fly commercially at least 300hrs/year for work, so let's use that as a base.
What does a Rotax 914 cost? $12.000 a pop, I seem to recall but maybe it's more these days. 2000hr TBO, so two engines running 300hr per year would cost: $3600, or $12/hr. Add another $1500 for insurance and that amounts to a total of $17/hr. Let's say $20/hr and it will include oil and probably any unschedule service.
On the previously trip that would have added $240 to the cost. Paying US fuel prices, this would increase the total to $618. Still cheaper or at least on par with a commercial ticket. Obviously for the UK example, paying UK fuel prices, this has now probably gone beyond the price of a ticket. But maybe some little hotrod diesel engine will come along and fix all that
