All I want is good action and adventure packed arc to wash off the bad taste that Wano arc left behind.
Oda likes to go back and forth with Zoro and Sanji. There is also the All Blue that he want to find. So, it is too early to speculate Sanji's or any other character's bounty.
More importantly, instead of comparing it with Roger's crew, you can compare it to his own crew. It can give you a better idea. Whatever his bounty will be, it would be close to Zoro. As it always has been.
Not a Sanji fan, but I thought it is an interesting point that you have completely ignored.