It doesn't help Russia. The end result is the same: A smaller pool of customers and an anchored price for the remaining customers.

In fact, Russia had to reduce their output because they refuse to sell it to countries that participate in the price cap and there isn't enough demand otherwise (also most of their flow goes west through the now mostly idle pipelines to Europe - It's MUCH harder to move oil east or south because the infrastructure in that direction isn't big enough to handle such a surge). So Russia's losing even MORE profits by refusing to sell to them. AND they still have to maintain the now idle pipelines to the West or else they'll break down over time and become useless.