Yeah, $100 seems fair and would really help those with 16 GB of system ram. If it is 16GB of GDDR6x, $700 for sure and maybe even $800 as it would be much closer to the 3080.
Depends if it's a 3070, or 3070 Ti. Your title states "Ti" but your poll only states a vanilla 3070. I'd imagine a 3070 Ti would be around a 10% step up in performance over the 3070.