In the case of late Soviet Union, one should not discount their inept economics: they've seriously tried to stop inflation at 0% and never increase prices despite growing incomes.

It has eventually lead to more and more goods' production stop being profitable and require subsidies. Which are then bound to have quotes.

It's not an easy task of planning anything where your populace wants both cars and shoes, but you have budget for only one item and have to choose.

Bloated defence budgets and large foreign-help funds did not help, sure.