Lemme try to help you out here

The original question is about size, but the Philosopher, for some reason, makes a detour into mass. This detour goes nowhere, and just ends up as a distraction to the point he's trying to make.

Larger breasts have more mass. His point was that just like how mass is irrelevant to the value of money, it is also irrelevant to the value of breasts.

It's also distracting that he says "you were to have $30 in coins as well". That makes it seem like it's important that Anon now has $60 instead of $30. If the idea was to compare $30 in coins to $30 in bills, a better wording would be "instead".

This is where reading comprehension comes into play. You have to be able to interpret what someone is saying, even if they don't phrase it in exactly the way that would make it easiest for you personally to understand. If you can't parse what they meant, that is indicative of poor reading comprehension on your part. It never says nor implies that the man having $60 matters. You're adding that to the story, and then complaining that the story doesn't address it.

The way it's written is like a trick question where the obvious answer is wrong.

The way it's written is meant to lead you to the understanding that while size (and mass, which is inexorably linked to size of living tissue) can vary, breasts are still breasts, regardless of size, just as $30 is still $30 regardless of denomination. It is a trick question, and being able to recognize trick questions is an important factor in reading comprehension.