Russia is just a sensitive b1tch at this point.
If it supplies Iran with SU-35 it pisses off:
Israelis,
Arabs,
Saudi Arabia cash cow,
EU,
US,
And now you can add Turkey/Azeribajian to the list
Now ask yourself for a few billion dollars does it make sense for Russia to piss off this many countries? Countries who buy much more Russian arms or have influence in geopolitics than a small Iranian arms contract could ever hope to have?
Russia only provides Iran with things it can mostly likely already produce.