Let's look at the numbers. I'll chose the capital of a country, out of many, that russia has harassed, stolen territory from, and is actively threatening at the moment, to make it a fair comparison.
Moscow GDP per capita: 22,060 USD 2018 Bucharest GDP per capita: 26,660 EUR 2018
Moscow average salary: 1100 USD 2021 Bucharest average salary: 1,614.91 USD 2021
If you factor in the massive gap between regular folks and oligarchs, and their employees, then the average worker in moscow is probably earning far less than that.
So, at least based on numbers, your statement of "better living standard in Moscow" is a propagandist lie you fall for. Even if Moscow is a Potemkin village, with big fancy buildings, the standard of living appears to be comparable to Bucharest, Romania, if not lower.
And Bucharest, thanks to russian dominance, is considered a poor city in a poor country in a poor EU country (Romania's per capita GDP and avg salaries are also higher than russia's).
His uncle should move to the US at least based on these facts. And if I may recommend, please, leave your country every now and then, so you escape putin's propaganda.