Yes. The phone, the hardware, is free. But you are locked into a two-year contract where you'll pay $100 each month for 24 months, which is $2400 total.
I bought my S9 directly from Samsung for about $700. But then I have no binding contract. So AT&T charges me based on my monthly usage of data. That's about $60 per month, plus or minus $10. So over two years my S9 costs me = 700 + 24*60 = $2140.
Not much different from your plan, but, a big BUT, I can opt out any time but with you're plan you cannot opt out without paying a penalty.