I've got an Amex Platinum, so Clear would be free, and I haven't bothered. I fly through AUS and DEN at least once a month, with MCO and ALB in there frequently, too. I've never been in a line long enough to make me want to spend the time to even research Clear.
FYI: the Morgan Stanley branded Amex Platinum comes with two cards and, I'm pretty sure, both get the Clear credit. Some benefits are per-account and some are per-cardholder.
I have the MS Amex platinum, and my wife is the free authorized user.
We get separate GE/pre-check credit, but only one $180 CLEAR credit
(Workaround as someone mentioned previously, through a frequent flyer program you can get CLEAR discounted enough to cover both family members)