The cost to the Russian people is high, but the cost to Putin and his entourage is yet another toothless freeze on overseas assets (the ones they know about), some irrelevant protests in Moscow, and a hefty increase in oil prices.
Isn't oil price increasing good for Russia though? Their oil isn't as cheap to extract so price increasing multiplies their profit very significantly if they can find a buyer.
The sanctions being levied against them will impair their ability to sell to a large portion of the world, including current (well, now former I suppose) trade partners in Europe. While they could try to undercut the global price in order to make their oil more appealing to remaining trade partners, it's going to be a challenge depending on how the current and future sanctions develop to even get to market.
A quick search gives this as the answer to who their largest oil buyers are: China, the European Union, South Korea, India and Japan.
China will do what China wants here. But South Korea, Japan, and the European Union will end up being harder to sell to, if possible at all, in the near future. India is a toss-up, depends on how they decide to participate in all this.
