If Ukraine and its allies succeed in inducing a soldier to leave the Russian army, that frees up money (namely, the salary that the Kremlin used to pay the soldier that left) that Russia can use to hire another soldier, so the only monetary cost you’ve imposed on the Kremlin is the cost of training the soldier that left.
Currently money is the most important resource for the Kremlin (probably by a large margin) and if the supply of young Russian men ever becomes the critical resource, then the scale of the war has increased so much that we should probably start calling it World War III.
If Ukraine and its allies succeed in inducing a soldier to leave the Russian army, that frees up money (namely, the salary that the Kremlin used to pay the soldier that left) that Russia can use to hire another soldier, so the only monetary cost you’ve imposed on the Kremlin is the cost of training the soldier that left.
Currently money is the most important resource for the Kremlin (probably by a large margin) and if the supply of young Russian men ever becomes the critical resource, then the scale of the war has increased so much that we should probably start calling it World War III.