The effectiveness of economic sanctions has always been about willingness and capability to last for all participants. Everyone loses in economic sanctions. Sanctions on Russia is going to be a long game for both sides and we are still at a relative mild stage despite some serious damage to Russian economy.
Neither sides has made any drastic/nuclear economic moves when it comes to sanctions. The west hasn't cut Russia off from swift banking system. Russia has not defaulted its loans and obligations to EU and the west. Anybody wants to know what happen last time Russia defaulted can read about the blowup of long term capital management and its resultant blood.
Russia is far from being completely isolated like Iran as long as China and other BRICS countries continue to do business with her. Convincing BRICS to join sanctions is currently very unlikely without some significant economic and geopolitical concessions from EU and US.
Even if Russia was completely isolated like Iran by sanctions, there is no guarantee that Putin would fold or Russian people would overthrow him as policy makers in Washington would like to see. Iran has been under sanctions for decades, no overthrow of government has taken place or any real progress on nuclear issues. In my personal opinion, if history is any judge, Russian people can endure more hardship than any other people certainly more than people in the west. They have endured Germany's attack in WWII, the economic hardship under soviet era and the pillage of its economy after its fall.
In the meaning time, we have a game of economic chickens playing out in backdrop of a great economic recession worldwide. Germany, EU's central core power only narrowly managed to avoid recession with 0.1% growth in the third quarter which can be considered as a margin of error in statistics assuming its statistics are not goal determined right from the beginning. Cross the ocean, US's oil industry, the only industry that is providing good quality jobs in good numbers for Americans are experiencing cutbacks and layoffs. How much longer can US fracking firms so loaded with junk bonds last when oil prices are below many of their production cost?
As for recent developments in Greece, it makes a mockery of the notion that EU is "unanimous" in supporting Russian sanctions since the new Greek government is clearly against sanctions at the expense of its farmers. However, I think Tsipras is playing a double game. Options to receive Russian loans reduces Brussels's leverage over Greece, giving it a strong position to negotiate more favorable terms from EU without worrying about immediate liquidity. However if Tsipras is successful, European central bank's balance sheet would be seriously impaired which would make continuing sanctions more difficult during market upheaval.
