Do you know where money comes from? No, not exporting oil and natural gas.
It comes from central banks. They create it whimsically. The Fed created $4.1 Trillion to claw out from the 2008 crisis. It was created from NOTHINGNESS. Thin air.
Russia has their own central bank. They are food self sufficient. They are oil self sufficient (the US is not, imports 9 million barrels every day).
If they want those planes, they just print the money to build them. If someone wants to adjust the ruble/dollar ratio in response, they can just remove the ruble from trading and peg it, like the Chinese do.
Don’t ever think money means anything special to policy. Central banks took all that over.
India will cheerfully pay for it. Go look at where they bought their aircraft from, go look at who they’re working with on their Brahmos missiles, look at where India got their tanks from, etc., etc.