Yes, that is it. It is certainly not perfect yet, but controls on who can obtain passports are sadly the norm in the entire world. And indeed the price of the plane ticket stays the most significant hurdle.
That's an understatement.
> controls on who can obtain passports are sadly the norm in the entire world
These restrictions are far from "the norm in the entire world".
Source? To prevent goalpost-moving, the restrictions we're referring to are:
The government will protect "human capital" in its decision-making, and travel can be denied for "national security reasons." Those deemed necessary to the Cuba socialist revolution — professionals such as doctors, scientists and engineers — can be prevented from departing.