I worked in the aviation refuelling industry for nearly 30 years and can agree with the previous reply, prices just kept going up and up, I had great sympathy with the local one man flying schools, they had great difficulty in keeping their prices at a reasonable level, do you remember the Diamond, both single and twin, they had modified Mercedes Benz engines we refered to them as diesels, this is because although a light aircraft they ran on Jet A1, something we had to be extremely carefull when refuelling, they unfortunately did not make the distance and fell by the wayside.
Howard.