Because the owners are driving around in big Porsches and have expensive cocaine and prostitute habits.
Or
£400 an hour for the plane
£120 an hour for the sim ( a new one costs about 150k and they cost a fair bit to keep running as they need to be quality checked every 3 months by an expensive external contractor.
£35 - £45 per hour for the instructor, which is a crazy tiny amount for a skilled worker, as an IT guy with relatively little skill I could bill cheap at £350 a day and the very best a really good IR instructor will get is about £150-£200
Finally, there's all the things you don't pay for like briefings, remedial instruction on attitude flying, teaching you what an NDB is and how to fly an ADF needle.
Quit whining, it's expensive, get over it
.