I think the main problem with SU lenses is not the quality control when they were made, but how they were treated through the years: we are talking about 40 years old glass that was cheap even when new and often was neglected or mistreated, while the Leica glass was expensive then and it's expensive now, so few people would dare to scratch the elements, or drop a lens etc...
RARELY I was able to find SU lense in NOS or mint condition and they always performed well, for instance the Industar in the previous shot is a '61, one of the first in production and it looks like brand new. I have another from the 80s with a sticky focusing ring and scratched front element that doesn't perform so well.
Another example is the NOS Helios 81 I used with my Nikon F2A to take this pic:
Good, isn't it?
This is the same subject with a Nikkor lens that has been used for long decades
I prefer the Soviet glass in this instance.
So...in the end for me it's a matter of choosing the right lens (being made of aluminium it's easy to see the ones who had an hard life) and buy from competent people. I spend $200 for my Orion 15 and I am satisfied with that wide angle, on the other side I agree that the price of a good Jupiter 3 is getting close to a Summarit that's the reason why that one along with the Russar is the only soviet lens I don't have.