You fail to touch on the 400 hours flown? if you buy a plane, let it sit, and never fly then its a bad investment.
If you fly 8 to 10 hours a month in a rental, that rental cash will go a long way to pay most if not all the expenses of owning a plane.
What I have seen is when renting its too easy to find an excuse to not go fly, when you own its so easy to jump in, go punch holes in the sky, lunch runs, or quick trips, when I quit flying I will sell until then I will own. If 100% ownership is not practical then a partnership, or flight school, set up right is very viable.
Look, nothing says a liability can't pay off, that's why we undertake liabilities for the benefits they produce, not their direct cash value, but it is a gamble, and if the benefit you are seeking is an increase in the cash value of the plane, you better be pretty damned sharp how you place that bet, because it's an infinite parlay to the day you sell, and is more likely to eat your lunch than pay off.
Now if we are talking about usage value, enjoyment value, the fact that there s no rental market that has what you want/need...
These are the issues that you need to focus on when determining if owning a plane is worth it. It basically breaks down to if you are buying a plane to provide a function, and you are willing to pay the reasonable costs to get that function, understanding that on any day you may have to spend $20,000 (or more) before you ever fly the plane again, or you have to sell it for salvage value (which in some cases is more profitable than selling it airworthy and flying).
If you are buying a plane as an asset, you need to put it in the extremely high risk section of your portfolio, and more likely than not, unless you are shrewd and active in the market and on maintenance, you will be disappointed by the performance. If you treat it as a consumable life commodity like a car, you'll be ok.
I'll put it like this, if you're comfortable sitting down at a hundred dollar blackjack table and can have fun playing for a few hours, you are a candidate for aircraft ownership. If that thought makes you queezy, or you don't have the resources to do it, or they stretch so far you're uncomfortable, you should back away from the table and keep renting at the $5 slots.