"그 맛에 하는거죠" == 그 맛 때문에 [그 맛에 끌려서] 하는 거죠.
=> (literally) I do it for that taste / I do it to have that taste.
=> I do it because I am hooked on that (attracting aspect / sweet part) / I do it because I am hooked on it.
맛 is taste or flavor, but also means other things like attraction, subtle effect, experience, etc, just like "taste".
(Ex: 인생의 쓴 맛을 보다: Taste the bitter side of life)
In this sentence, 그 맛 means the aspect of whatever is being talked about that attracts him and makes him do it.
It usually means something specific - rewarding feeling afterwards, the pleasure of doing it, public recognition, etc.
So you need the context to have a more accurate translation, especially as to what "그" (that) refers to.