It’s still small change and symbolic. You can’t do economic sanctions on a country with that much land mass and resources. It would be harder than putting economic sanctions on the United States.
You can, you just probably wont keep them. Russia is a natural resource exporter, if the west doesn’t buy their assets, china will.
Putin should just get it over with and send his whole army into Crimea to crush the Ukrainian one. The euros and Obama will throw a fit but ultimately do nothing. Backing down on the other hand will hurt Russia’s gains.
If I were Putin I’d take the territory and wait out the ‘sanctions’.