Moscow started offering 1.9million rubel in July, now Belgorod goes to 3million rubel a few months later. That is a more then 50% increase within 3 months. It is also not just a token amount, but multiple years worth of average Russian salary.

So no it is not sustainable as Russia has to raise rates and it shows very clearly how much Russian men actually support the war. It also is not as cheap, as offering high salaries in the military, means all other employers have to compete with higher salaries as well. That obviously causes a lot more problems.