ROI should absolutely be a part of calculation, else it would be easy to spend (even) more money on a home that's not desirable or enjoyable. The return is just not limited to money only. You likely want to get most house for your money, by various metrics.
I don't think that homelessness has much to do with construction costs: homeless people are usually not those who have $70k lying around which is not sufficient even as an initial downpayment for a home. The lack of housing is real, but it's more about regulations which forbid to build "cramped", "ugly" houses or "slums", or anything at all near elite houses which may not go down in "value".
"Investment" in this context is personal investment as a primary residence. You seem to be purposefully missing the point or cherry picking a singular definition of the word. The OP is literally a book about how to build a good home for yourself that is affordable. I'm fairly certain 90% of the audience on HN understand the housing crisis that exists and no one here is arguing for more rent-seeking with this book.
ROI: Return on investment (ROI) is a performance measure used to evaluate the efficiency or profitability of an investment or compare the efficiency of a number of different investments.
What do you think it means? "Enjoyment of my property" is an important aspect of a Cost-Benefit Analysis but it's not ROI.
Anyway, it a is a singular problem in an otherwise laudable process.
Using that definition, “efficiency of an investment” is quite apt for the characteristics of a home which do not involve monetary return. In other words, I want as much X for every dollar I put in. X can be comfort, curb appeal, U-value, etc.
I don't think that homelessness has much to do with construction costs: homeless people are usually not those who have $70k lying around which is not sufficient even as an initial downpayment for a home. The lack of housing is real, but it's more about regulations which forbid to build "cramped", "ugly" houses or "slums", or anything at all near elite houses which may not go down in "value".