Property taxes are ordinarily a percentage of the value of the land and structures because in most cases it has some approximation to services consumed. A building with twice as many condo units might require twice as many police, create twice as much traffic, etc.

A large data center could plausibly be sitting on a piece of land worth a million dollars and then have a billion dollars worth of equipment in it, but still not require any more police officers or traffic lanes etc. than the million dollar piece of land sitting next to it. It might even require less.

It's easy for a town to come out ahead from that even after providing significant tax breaks. When you have something consuming the same unit of services while having an assessed value of 1000x the typical amount, what percentage tax break they would have to get before the government isn't coming out ahead?

You're missing the point. Towns come out ahead when the people living there come out ahead. I'm not arguing with your math, but your math is also a straight line to a town with no people at all being better. Towns are for _people_.