If you wanna play 100bb on 888 2nl you need to play the full ring tables, I am not sure why they have all their 6max 2nl tables to be 50bb buyins but they are and its only for the 2nl tables. Unless you play the snap tables which are 6max and 100bb buyins.
In general to setmine you need 7.5-1 odds
since you will hit a set that often, generally however to make it profitable you want your opponent to have about 15/16x behind the size of the bet you need to call since you could easily get no action when you flop a set or run into a set over set situation etc and get little return or lose a stack in the set mining attempt.
Basically that means if its opened to 3xbb you want them to have 45-48bb behind which means setmining with 50bb stacks does provide roughly the correct implied odds, and even more so if there are a number of opponents to the flop where it increases the chances you get paid off when you hit your set.