I don't comprehend what makes them think that sanctions, never before used on such a scale against the UNCS veto player possessing ca. 20% of the world energy resources and even bigger share of weapons, would work better this time than, say, in Iranian case, where Ayatollah regime appears to only strengthen under external pressure, inevitable technological archaics aside?

Russian self-imposed autarky could, realistically speaking, be nothing more than sound and fury, sure. But its current economic model already differs greatly from North Korean, Iranian, Cuban, and former Soviet. The market forces are in play there on a level that all countries in this list could only dream to aspire. The main Russia's problem of the past lay in its chronic inability to manipulate through soft power. They're learning, though, simply because this time Russia, unlike USSR, is much more open to the world from the informational PoV. Herein lies the rub of relatively cheap and effective Russian propaganda discourse.