I feel like an assumption I come up against a lot with liberals is that the USSR had basically the same ownership class structure and wealth distribution that similarly developed capitalist classes had. I tried Binging this but don't have a good sense of what authors to trust.
"Wealth" in the USSR is probably going to be hard to quantify. I mean, guys like Stalin, Khrushchev and Gorby all pretty much had very modest means. None of them had secretly stashed wealth - Gorby had to make Pizza Hut commercials and do speaking tours to make ends meet. And you're talking about the absolute upper eschelon there. I think if you're dealing with someone who is focused on the wealth of party leadership, you can actually find out what personal wealth they had, but it wasn't much. Libs will point to the fact they access to personal cars with drivers, lots of travel, meals made for them, etc, but a.) none of that is "wealth" and b.) that's the same access that even low-level politicians have across the world.
If you're talking to someone about more societal inequality, you can look at ratios of pay between workers and high-level managers. In the GDR I seem to recall this ratio was 3:1 but don't quote me on that.