Shouldn't you also take into account that Climbee saved around 105,000 euros in rent over 20 years?
However, she still paid for housing through repayment and interest – how long and how much exactly, I don't know, you would have to know too many parameters, which probably won't all be exactly known after the time anyway.
Let's assume that she wouldn't have been homeless and definitely would have lived somewhere, for comparison you have to consider the delta between rent and repayment during the repayment period. For that, you need to take a fictitious rent if you own the property or a fictitious repayment if you are a renter. She would have had to spend the money either way.
In the case of ownership, it goes into the equity stock, with which she can later calculate her annual return. In reality, you don't calculate x% p.a. on the equity that existed at the time of purchase. That's just a rough simplification. With every installment paid, your equity increases while the period for your calculation shortens simultaneously.
There should be Excel sheets on the web about savings plans with a duration of so many years, which are periodically funded and already interest the euro deposited on the first day with X%, then grow exponentially through compound interest, but also have a linear component due to regular deposits. This is how the apartment should be seen during the repayment period. Only afterward does a “rent-free” period arise, which can be fully credited against rent that would otherwise have to be paid.
Then you have the increase in value upon sale, which, calculated over 22 years, is not that high a % p.a., as I have calculated. Minus repairs, minus inflation, minus interest costs. Plus rent freedom in comparison to a fictitious rent (previously you set the delta here) from the last installment onwards.
That results in something that allows you to calculate a % p.a. return after sale. This is then compared with alternative investments. And then keep in mind that Climbee was able to make a very strong sale in a boom period here, which is certainly not given to everyone.
This is like buying a Golf in 1995, driving it for 20 years, and selling it for twice the original price.
Here lies a fallacy: For this Golf you would first have had to save equity, for example liquid as a daily allowance account. You could have made your savings plan smaller but started earlier if you had simply bought a different car that you can only sell after 20 years for the simple purchase price (this would be equivalent to a rental apartment). Repairs, interest, you don't have to deduct.
With the Golf, you also had to pay one or the other repair yourself over 20 years, so your resale value is not net at twice the price, as you have to deduct that. Then minus interest costs, because you financed the car (equivalent to the apartment). Then minus inflation.
All these negatives are already included in the fictitious rent, i.e., the comparison value
already included(!!), so they do not have to be deducted a second time.
To stay with your car example: With a price doubling after 20 years, after deducting the costs I mentioned above, you might get out 1.4 times. So +40% in 20 years. As % p.a. that’s not great, really not. Just 2% inflation p.a. eats away 30% of your "doubling" in 20 years alone, before you have deducted anything else.