Those prices are genuinely and thourally awful. I pay a ton of money for an AT&T small biz line (and watch, and laptop lines) and I get actually-unlimited data for $90 (used to be $80). But you can get a prepaid line through AT&T prepaid for $60 (I believe) that has “unlimited” until 22gb where you are deprioritized until the end of the month. Or cricket, an AT&T-owned prepaid company, has a (supposedly) actual-unlimited option for about the same price, but they limit devices and a few other things.

9gb for the ~same price is highway robbery.