My point is that nobody doing that would be doing it for free. This applies the apologia for all other empires to Russia. I.e. that empire builders do it sometimes by accident but always for benevolent reasons. That's incorrect. Empires are built by extracting wealth and to extract wealth.
I think you agree with this as I'm reading your second paragraph as sarcasm. If you do agree, then it's not possible to conclude that Russia will lose money. It may do, if it loses, although even that is questionable. If it wins, it will gain wealth. Or it's capitalists will do so. There's a contradiction between your two paragraphs.
If Russia's motivations are imperialistic (I haven't seen evidence for that, myself, but it depends on one's definition of imperialism), there would be no point if it cost more money to achieve than would be recouped after. Until it's over, it's not possible to say that it's already lost money. It's costly, but that's different, and doesn't answer, 'Costly for whom?'
(Please don't misunderstand me – I'm not saying that Russia will not exploit whatever parts of Ukraine it keeps hold of. It's capitalist. Of course it will. I'm suggesting that this war doesn't amount to a land grab simpliciter.)
One counter to this is that the US is spending money to ensure that Russia does lose money. Time will tell whether I'm right or wrong but I think this drastically overestimates the strength of the US. It doesn't have an industrial base (except in vassal and puppet states). So it cannot match Russia's military output.
And the industries the US does possess are governed by the logic of finance capital not industrial capital. Money spent does not indicate how much has been bought. $10bn spent on weapons, for instance, doesn't mean you get $10bn worth of weapons by the time you factor in all the sales teams, admin, embezzlement, and middle managers, etc.
The US seems incapable of providing Ukraine with the arms that the Ukrainian military is asking for. It's publications have started to admit this more and more. Due to the above-mentioned logics, the US doesn't have the intellectual-ideological or industrial capacity to ramp up manufacturing. The US certainly has people bright enough to figure it out but they're inconsequential in the face of a military-industrial complex designed to make as much money as possible rather than to 'win' wars.