Because of that high cost, the whole Nord2 argument against is pretty tough to make if Putin isn't rattling sabers. Its kinda all kinds of stupid to do this now. Its the irrational that is worrying in this situation.
If Putin is doing this because of some sense of terminal urgency it may be very ugly. For starters, we may well have to arrest all his oligarchs and freeze their accounts. He doesn't want a proxy war where the West has a huge open border to supply weapons and INT to a motivated Ukrainian population, perhaps where Poland and Romania also supply well-equipped troops.