The question is how much it will cost Ukraine? In my opinion the conflict is already lost, now the Ukraine should concentrate on minimizing the losses and avoiding full scale war.

that's exactly what will happened it will cost russia so much more than they could possibly imagine from just Ukraine pushing back alone

But what does Putin care what it costs Russia? As long as he personally is still well off

If it bombs their economy and puts pressure on the oligarchs, the chances of overthrow/revolution goes up.

On the other hand, if this stirs up nationalistic sentiment, his support will go up.

I am not sure how these net off.