I thought it was clear (though obviously not) from the example that it was an idealised case, where "ownership" was referring to exclusive use. Your counter-example does not fit that simplified model - you are effectively describing a case where there is one car per person. The premise is not that "wasting money is wasteful", but rather that unequal distribution of resources is wasteful.
It is not the case that all investment is done by wealthy people - large amounts of investment is carried out and directed by governments. Indeed, my understanding is that, if one properly accounts for failed enterprises, there is no significant evidence for greater efficiency in private markets than public ones, both in terms of time-averaged economic growth, and in terms of generating large technological improvements.
It is not the case that all investment is done by wealthy people - large amounts of investment is carried out and directed by governments. Indeed, my understanding is that, if one properly accounts for failed enterprises, there is no significant evidence for greater efficiency in private markets than public ones, both in terms of time-averaged economic growth, and in terms of generating large technological improvements.