The honest answer is, it depends on the gecko. If their tails are fat, then their weight is fine. I think folks are a little too eager for obese geckos these days...obesity isn't healthy in the majority of species, and I can't see any reason to believe it's healthy for leos, either.
Some leos are naturally smaller, some are larger. The frame of their body is going to make a difference in how much they should weigh--a shorter, lighter built gecko shouldn't weigh as much as a longer, sturdier one.
I don't think a leo's tail should be as big around as its body, and I don't think they should have wattles of fat under their arms. That's just my personal opinion. 
My animals aren't that obese--they keep their weight remarkably well through the breeding season, hardly losing any noticeable tail fat at all. I pay attention to their tail fat, not to the gram scale.
Most people say that females should be bred at 50 to 60 grams...I say 40 to 50, but it depends on the overall size of the female, her age, and the condition of her tail. If she's 3 years old, has a fat tail, and doesn't quite weigh in at 50, she's still fine to breed. I don't feel a need to feed her wax worms until she waddles, just to meet the arbitrary weight requirement.