We ran a helicopter trip to Moscow in 2016 - it was a complete epic (ended with getting an IFR formation clearance to Moscow from Belarus for R44 helicopters!).
Two impossibilities in one flight!
My general feeling was that we were extremely lucky to both get in, and get out! The reasons for the (indescribably high) costs were not just opaque but completely invisible - but we got what we paid for so the system worked. I heard afterwards that we were the only private helicopter trip (not state-supported) to ever get to Moscow (most end up waiting at the border for a few days until they abandon and go home).
Beautiful country, great people, nearly impossible by both financial and paperwork measures - but a great trip!