Does the first joke refer to the fact that if they wanted the Ferrari they’d have bought it already, or that if they really wanted the Ferrari, they’d have chosen a more lucrative profession than economics?
More specifically, the first one is a dig at anyone who tries to infer preferences from behavior, without considering or knowing the full set of alternatives available to the individual.
In this case, even a well-paid tenured economist probably could not afford the Ferrari without making some significant sacrifices elsewhere. So it's not that they are choosing between "Ferrari" and "no Ferrari", it's that they are choosing between "Ferrari and I don't have any money and my wife leaves me" and "no Ferrari and I keep my retirement savings and my wife doesn't leave me."
The relevance here is that, for some people, their best option might actually be "stay at horrible job at Amazon where I'm forced to piss in a bottle", not because they like pissing in bottles, but because the alternatives are actually worse.
The only thing you can tell from a person's behavior is that, to that person at that particular time, whatever they did/chose seemed like the best option.
