The possible economic sanction we might see on Russia is US and other allied country will stop dealing with Russian product also with other services. And this is totally huge if US allied country will follow but I don't think Russian government are afraid on this since remember they also have allies and most provably they don't need US since they are already have ways to boost up there economy that's why there government is brave towards decision making on what they think beneficial to them.
They have enough energy to actually cause trouble for Europe and that is what they are trusting on. If you put sanctions on Russia and do not sell them anything, then they will stop giving you energy. Which means that Russia will suffer because they can't get anything from outer world but they could work with China which we all know could end up helping them financially and give them whatever alternatives, maybe Russians can't get iphone but they can get Huwaei and that's the type of situation Russia will be in and that is not ideal but not horrible.
However, Europe will be losing energy and that is not something they could get alternatively, they have some themselves but they were getting more from Russia and they will be lacking that. It would be worse for Europe then it would be for Russia.