There were no such drastic wealth differences under Soviet socialism and for the most part there aren't any in AES states today (between the party and the people that is; naturally there are very rich people in some AES states but they are not party officials and they got rich through private business). Where corruption has historically tended to creep into socialist systems is with people in certain positions getting privileges in terms of access to goods and services. Of course the fight against corruption is always an ongoing struggle in any society, it's just that under capitalism what would be seen as corruption under socialism is fully legal and simply called lobbying or doing business.

When we speak of privileges we must be clear about the fact that simply being wealthy in a capitalist society offers you vastly more unfair privileges over the rest of the population than being a party official in a socialist state ever has. Under capitalism nobody bats an eye when poor people are not able to afford to buy the kinds of privileges that rich people can. Socialist societies at least make an attempt to correct the most extreme disparities of capitalism, the worst of which is the ability for the wealthy to buy political influence and to override the interests and the will of the majority.

This is why we do not speak of socialism as being the equal distribution of wealth, which is the erroneous idea that liberals have of socialism, but rather of the democratic dictatorship of the proletariat over all political and economic spheres of society which is the true essence of socialism. By contrast when the liberal speaks about either socialism or capitalism they always fail to apply class analysis and instead reduce everything to the level of the individual.