If you're spending >$1000 on tires, how is a $80 set of TPMS hard to justify?

Presumably you're buying snow tires for safety reasons. Proper tire pressure is important for traction, thus safety. And winter is the time when tire pressure fluctuates the most.

Sure, but if you’re the kind of person who buys winter tires (which IME is pretty rare in the widwest USA), you probably know that and check your pressure every couple weeks. And it probably only fluctuates a couple PSI which is well within safe bounds.

> And winter is the time when tire pressure fluctuates the most

genuinely curious, why? I thought tire pressure fluctuations were linearly related to air temperature fluctuations. does the temperature vary more in the winter than in the summer?

At least in some of the US, quite a bit more. Winter might be swings of >50F, especially night to day, while summer variation is likely to be <40F. I'm not what all weather patterns factor into that, but a major part is that winter air is dryer, and water vapor does a lot to 'buffer' brief temperature changes.

That said, I mostly end up checking my tires more in the winter because I care more; if a tire is only a few pounds low I'd still prefer to handle it before I have to go drive on snow during a cold snap.