Wouldn't it still be a savings on the FICA regardless of how much more you ended up making?
Well, the income limit on Social Security for 2018, is $128,400. Meaning once you get to that amount, you are no longer paying Social Security taxes on income above $128,400. Using that figure, if you had an LLC treated as an S Corp for tax purposes, if you paid yourself 50% of that amount ($64,200) as a salary and the other 50% as a distribution, you'd only be paying FICA taxes on the salary portion and not the distribution. So instead of paying FICA on $128,400, you'd pay it on $64,200. Thus saving $9,822.60 in FICA taxes (15.3% of $64,200). The reason is you don't pay FICA on distributions.
The point I was making in excess of $250,000, if you split that in half ($125k in salary and $125k in distributions) you are virtually maxing out FICA taxes and thus no real tax advantage by having an LLC treated as an S Corp.