Plus, every dollar spent on Ukraine buys a lessened chance of other nuclear powers trying to invade their neighbors willy-nilly. If Russia is allowed to just invade whomever they want with minimal pushback from the world, that just emboldens more wannabe Putins to start wars of aggression or worse, build up nuclear arsenals.
The only principle the GOP has is whatever they think will win them the current argument. Asking for any ideological consistency from them is tilting at windmills.