"For all I care" generally has the same meaning as "As far as I'm concerned" but is definitely more informal, aggressive even. I have found quite a few sentence fragments expressing "As far as I'm concerned" but none of them seem to have the bite of "For all I care".
- по моему рассуждению
- насколько я могу судить
In very general, you use this in situations when you refer to someone you either don't like or who made you angry, and the part of the sentence after "For all I care" is always referring to something the speaker considers to be a bad choice. Often, the speaker doesn't really mean it but is just being sarcastic.
- "For all I care, you don't have to protect your head at all" (when driving the motor cycle)
- "For all I care, you don't even have to get out of bed today" (thereby missing something very important)
- "For all I care, you can keep paying twice more than everyone else" (when it would be so easy to change that)
How to express the same in Russian?