In the west, trade is guided by the old Polish saying: "Let us love each other like brothers, but count the money as Jews do."

As you mentioned in one of your previous comments, Russia gave Ukraine preferred pricing for gas and oil in exchange for staying in the Russian sphere of influence. How that sphere of influence works, I explained on the example of minicomputer K-202. When Ukraine sought more economic freedom in handling its affairs, Russia used Ukraine's dependency on Russian oil and gas to influence politics in Ukraine. It is just a modern version of tactics used during the Tatar Yoke on Russian principalities.