When shortcomings of socialism create a public need for goods, private trade will provide.

NEPmen :
"NEPmen were businessmen and women (NEPmenshi) who took advantage of the opportunities for private trade and small-scale manufacturing created by the New Economic Policy (NEP). Their entrepreneurial activities, indeed their very existence, were an affront to the Communist Party and its goal of building socialism in the USSR. Yet, so long as state commercial and cooperative institutions were incapable of meeting the demand for goods and services, NEPmen were (barely) tolerated. Often depicted as fat, greedy, and in certain renditions, Jewish, NEPmen quite literally embodied the contradictions of a policy whose aim was to build socialism with bourgeois hands." - http://www.soviethistory.org/index.php?page=subject&SubjectID=1924nepmen&Year=1924&navi=byYear