It included brakes, an alternator, an upgraded navcomm, a new mag, new AI etc. Rentals have to pay commercial insurance, which is a big cost item for them. It is VERY difficult as a private owner to fly a C150 and have it cost you $100/hr, unless you fly 10 hours a year (or park it at Signature and use their shop for everything). I flew 60 hours/month.
I bought a plane with almost 0 time engine, had I flown all 1800 hours until TBO, I could've bought 3 engines with just the savings vs. renting. Your engine math doesn't work, because assuming a VERY high end overhaul for O-200, 18000USD, it's only 10/hour for the engine "fund", and the plane does not lose 18000 of it's value if the engine is making metal. A $22k 0-hour 150 is not a $4k 150 if it needs an overhaul, it's more like $10-12k 150, so the "effective" engine fund is more like $5/hour.
I understand your point that in some cases, if the plane is just a "toy" or something you use every now and then, and you intend to keep it in the long run, it is a slightly depreciating (but not as much as you'd think) asset. But for active use, I don't see it that way.
Yeah, insurance is insane for the commerical operators, agreed.
Your math works out well on the smaller aircraft. On some of the larger ones, the engine replacement is a bigger percentage of the value of the overall aircraft.
And no disagreement at all in the "active use" thing. The more they're flown, the better ownership becomes.
I think it's possible in both the rental and the ownership cases to rationalize away some things because they're "uncommon" or whatever, too.
Examples might be aircraft that someone buys with very advanced avionics that work they day they buy them, and then the unit craps out, no warranty. That happens. Plus the usual instrument replacements (not including upgrades) over time, etc.
Have been watching my CFIs fleet and his expenses over a year's time with an interest in how he does things, and an electronic HSI and a Turn Coordinator tacked on $5000 to his operating expenses on the three aircraft in the blink of an eye. Running a small commercial fleet doesn't appear to be for the feint of heart!
Being deeply involved in a typical club, not a school, as a volunteer, is probably the best way to see what costs really are on aircraft, and I did that back in the early 90s... so ownership "stuff that comes up" was less of a shock for me than some folks I've met who had bad ownership experiences. Most of it was their own "not knowing" about stuff that happens.
Example: Went to fly instrument stuff with
@jesse years ago in KLNK and a couple days in, the nose strut gives up the ghost and goes flat in the -10F temps. Wasn't "planned" per se, but wasn't expected either. After you've owned for a while you just shrug and get out the checkbook. But that becomes a number on the hourly cost of operation spreadsheet.
I do think you overstate the engine worth thing a tad, though. I wouldn't pay more than $10K for a 150 that was actually making metal. I'm sure someone would, though. I think you'd see most buyers offer $8K and pay $9 depending on the rest of the airframe and installed avionics which is usually nearly nothing on a 150 unless someone shoved an IFR GPS in the panel. "Ain't much airplane there" if the engine is toast. But I do see your point. People often buy "hope" over hard numbers.
And that's the real story on all of this. We all WANT to fly so we'll often let emotions get involved in aircraft purchases or operational costs. Like our co-owner who left this year said, "My heart says stay, my math says no."