USSR??
Never heard of the minimum wages for factory workers, minimum wages for ship crew and officers, minimum wages for doctors, minimum wages for lawyers, minimum wages for bank clerks? Those are called national or category contracts, or agreements, and are valid nowdays, the great free market era, to regulate the market.
The pilot category is one of the many, unfortunate catergories without such a baseline agreement, so virtually a pilot can work for free, without anything being illegal or immoral.
D