IIRC Russia signed the Budapest Memorandum in 1994, guaranteeing Ukrainian sovereignty in return for Ukraine giving up its nuclear weapons.
If anyone is paying a price, it is Russia.
* Inflation at 8.6%
* A pariah state
* An army that is a laughing stock. Ditto weapons. Riddled with corruption.
* No foreign investment, except maybe the Chinese. Good luck with that.
* Half a million dead. Human wave tactics.
* Gas market to Europe - gone. Oil market severely restricted.
* Primitive technological manufacturing capability. No-one knows if their nukes will even work.
* A ruble no one wants, not even the Chinese.
* An ageing workforce of scientists and engineers.
Another 5 years of war in Ukraine, IMO Russia will be a failed state. Even if it stopped right now, it would take decades to rebuild to before 2022.