While Ritika has a theory that it was Ram's mother from whom he inherited all the money from while his father was just safeguarding it for his son, and hence had no major control over the finances till Ram could take over (after he reached of age/father died) I think it's coz his finances were always controlled so that he learns the value of money and doesn't become a privileged kid like Shubhu and Shivina.
I refuse to believe that it was Ram who earned all that money, not because Ram cannot do it, but because Ram shows that he has grown up in riches, from being dependent on househelp to not knowing how to do simple chores, and yes, a person can unlearn such things in 10 years, but isn't it just convenient.
Also, if Ram comes from an affluent family and Priya from a middle class, it explains why Nandu accepts Ram but not Priya, else she would not have cared about him at all, and would have left the second Kapoor senior died, her staying shows that they was reserve money that she could use till Ram took over.
Ram and Priya are contrasting characters, and their approach to financial situation is one of the key highlights of the relationship, it has been from the very start, so I think if they are driving home that Ram was actually poor, they are ratcanoning everything they have established so far.