Oh boy you're not gonna like my stance on morals :)
And I'm not sure if I should get into my philosophy on language... But, si je parle en francais a tu, it's as useful as if I hadn't talked at all to you all, because (assuming you don't already know French, if you do, replace the example with a language that you do not know and the point still stands) French is a social construct amongst the French, not amongst English speakers. So therefore, different constructs have different values in different contexts.
I guess my wandering point here (because I absolutely agree still with the original poster that money is a made up social construct) is that even though you value money more than robux, it doesn't give money any more legitimacy, it's just you've decided one is more useful than the other based on the necessities of society. That is not a wrong thing to do, by all means, you need money and not robux to survive in common society, but it does cover up the nature of things in that money is technically just as legitimate a token as robux.