A fair point. However, those are all relatively fixed. A car dealer needs to buy a new car to sell one. They don't necessarily have to invest more in the items you mentioned to grow their revenues.
TLDR: businesses that scale vs those that dont : )
Well, the flip side of your argument is that since "his inputs are only time," then he only has a fixed amount of time to make money from. Whereas, as long as the car dealer can sell every car he buys, he just has to keep buying cars in order to increase his revenues. Clearly there's more to both of these statements than that, but that's the point!
In any case, roel_v is pointing out that revenue isn't a very good metric without more data to evaluate it.
I'd like you to provide an example of a business that doesn't scale :-)
I hear you. I don't find the argument that robust given that everyone is limited by their time - car salesman included - but I hear you.
Agree that more data helps. For a headline I'd rather see revenue than margin or profit, as those are more subjective (or net revenue, if you're selling goods).
Unscalable business? Obviously a subjective take but, to me, that means anything where you're charging by the hour (e.g. consulting).
Agreed that's simplistic, but it's a starting point.
Assuming taxes, office overhead, other processing stuff, keeping profit overhead in place, etc, one could still be paying 3 people $5k-$10k/month with room to spare.
TLDR: businesses that scale vs those that dont : )