>As a US citizen returning to SFO I have spent anywhere from 30 minutes to 2 hours in line.

So, given the procedure (and the non reimboursable fee of US$ 100)and depending how distant you are from an "interview center" (and how long does the interview take):

https://www.cbp.gov/travel/trusted-traveler-programs/global-...

I would say that a "make even" point could be around 3-4 international travels planned per year (given that the program needs to be renewed after 5 years).