Chances of getting a legendary are exactly the same (unless you're pulled enough without getting one to be into mercy):

0.5%, or 1-in-200 for an ancient or void

1% or 1-in-100 for a primal

6% or 1-in-17 for a sacred

25x ONLY means that IF you get a lego, it's 25x more likely to be the lego you picked instead of one of all the other legos available