Yep,
@jeff3820 , I was going to mention this.
Although in the case
@Sequoia225 mentions, his provider (TMo) doesn't have adequate coverage, so it would require a switch.
I was a really-long time ATT customer (20+ years, until a few months ago), so I'm a partial-mod on their forums, and used to help people do all sorts of cost-analysis like this, up there (including publishing some cheat-sheet type stuff), and their network is great for most rural stuff.
In fact, Verizon is actually worse for most of our rural, in the PNW, but ATT sort of hosed everyone who had non-carrier devices, at the start of the year, so we moved, to the only other carrier with halfway-decent rural coverage here (I literally live 5mi due-N of TMo HQ, too, but their rural coverage is abysmal, just 30mi of town, otherwise I'd be with TMo, fingers-crossed on the merger, which should improve things).
Most people who have any kind of unlimited plan have a LOT of LTE-tethering data, typically 10-15GB, at least, some as much as 50-75/per-device, depending on the carrier/plan, and most just reduce you to 2G speeds (still pretty usable, for most things), after that (we have a combined 75, between our 3 devices, for example), after that.
In this case, it
might be cheaper to just move to ATT, from TMo, but it's hard to say, it depends on what kind of deal is already in-play, 19 for the unlimited hotspot is a pretty good deal.
I wish ATT had similar deals for a regular hotspot device, but they limit their "screaming deals" like this to car-hotspots, for the most part (because they realize people are unlikely to really saturate their usage from the car).