Parshas Ki Tisa

Shmos(30,11-16)1. Why is counting the Jews a sin to the degree that everyone has to redeem their life if it's done? In answer to this but also in what would seem to me to be the simplest meaning of the words I'd like to suggest that the word "Pakod" and all it's conjugations should be translated as "remember" or "redeem". In Bereshis (21,1) we find "and Hashem pakad Sarah." There it's translated as remembered. According to this translation of the word, here it the concept would be a mix: The counting in itself is not a sin. Though when each Jew is counted he is "remembered" by Hashem. This is done by evaluating where he is holding in life. This could result in a decision that he is deserving death, so we are commanded to give the shekel, just in case. The next possibility would be sourced in the end of Bereshis (50,24) where Yosef tells his brothers "Hashem will redeem you and take you out of Egypt." This would seem to fit here best since then the whole thing is a command about being redeemed. Though according to this, why are two different terms used for "redeem" (kofer and pakod)? Additionally we end up back to the first question of what are we being redeemed for? If you say it's just a general redemption for the wrong we've done, why would we all give the same amount and when would we give it?