This is becoming a far too expensive war for Ruzzia.
Yes, the stakes are constantly going up - Ukraine has failed to prevent war (it had at least 4 months to do something - starting with direct negotiations or outmaneuvering Putin by providing unconditional amnesty to separatists - just like it happened with Chechnya), has failed to solve it at the start - when the costs were low. So now, when the costs went over the top and Ukraine stays bold on its desire to ruin Russia - Russia has to justify the resources spent for this conflict, and the "justified" mark is constantly moving upwards towards total elimination of Ukraine as a state.
"Peace talks" now for Ukraine equals death (at least "political death") for everyone at the top - their actions have caused lots of losses, they've spent enormous amount of resources and credit costs without any real achievements. For Russia - it'll not look like a victory either as the initial political goals were not achieved and are as far as never before. Though I believe the real goals were by far not the ones declared - give a "magic kick" to industry by forcing outsiders run out and prepare for the next "modern" war. Yes - this conflict is simply a costly preparation to the next.
You are thinking a mixture "martingale" style and sunken costs fallacy - Since Ruzzia's cost is going up, they have to double down on the cost to try to achieve a bigger victory. Now, why don't you try playing Roulette with that mentality? Or anything else for that matter (options, shares, ...)? The fact is that is that Ruzzia may simply not be able to reach the great objective of suppressing Ukraine as state and should probably be thinking at this point of leaving the table.
But you are right in one thing - that is the Kremlin mentality, double on the bet no matter the cost, no matter the effort,... if a tyrant gets it wrong, people may be getting strange ideas about who should be in charge uh?
Ukraine failed to prevent the war? You know that Putin's "proposal" for peace included basically getting Ukraine to have no army nor any means of defence? Who in his right mind would accept to be pre-defeated so that Putin had an easier time invading. I think someone in the Kremlin had lost it to even propose that.