As a comparison with another stealth program, the F22 (like explained by CM) only flew 160hrs/perplane in 2012, a considerable amount of the training is done on F16's.
Also interesting to compare flighcost (yr2012)
F15 vs F16 = 42,000$ vs 22,500$ two-engined vs 1 engined (same type F100) MTOW about 80% more for f15
F15 vs F22 = 42,000$ vs 68,000$ = +60%(F22 also promised to be cheaper BTW)
So where do you think the F35 will come given the fact that it is in the same weightcategory than the F15, has the F22 engine type with a lot of upgrades and also at least the same level of complexity increase than the F22 was over the F15.
I would suggest a number close to 35,000 is very conservative, 40,000+ might well be closer to the trueth.