If one has to explain a joke then either they're bad at it, it's a bad joke or they have the wrong audience....I'll leave the conclusion as to which is it to the readers :)
The article is about making money (even from the title)..the commented upon line is insinuating that if you think the article isn't for you (ie you just randomly stumbled upon it), then you obviously are not interested in making money...sarcasm :)
Oh for sure, I grew up poor and am now on the other side. But that’s not what the author is talking about. He’s condescending to people that are making $250k/year for ”leaving millions” on the table. At $250k/year you don’t have to care about money a whole lot, and you can make that being a developer.
This line is distasteful and detracts from the rest of what you wrote.