[FARS]

Last count there were about 40,000 Russian consultants operating inside Iran in almost every facet of technical life, construction and industry. Plus consultive roles.

Their salary/earnings every month are quite significant an income flowing into Russia as much of it appears to do.

[PsyOp]

One report I read (perhaps Alibeks book) talked about an Armaments trade show held in Moscow in the late 90s. Attending the show were Iranians. In addition to conventional weapons and the techs to maintain them, they were very open about their desire to hire chem/bio weapons specialists and chemists trained in their manufacture. The monthly salaries they were offering were equal to (or exceeded) what these people made per month before the collapse of the Soviet Union.

As you stated, I think the reason the Russians don't want to help us with the Iranians, is the same reason the Mexican govt thumbs their nose at us. Russian in Iran, like illegals here, are sending to much hard currency to folks back home.