Estonia, Latvia, Lithuania, Serbia, Turkey, Bulgaria, Hungary... (I suppose some of these might also be considered Northern/Central Europe, apologies if calling them Eastern-European is incorrect, if that's what you were getting at. I tend to make the mistake as I'm in Germany and it's easy to conflate "Eastern-European" with the other European countries that are... well, to the east of us.
)
Basically, what I meant is that Steam introduced regional pricing - tier 2 pricing for some of the economically weaker European markets as well as a whole separate tier just for Russia a couple years ago - and it's been paying dividends.