formatting link
> $27 each. I think I'll use film.
Nothing strange, just a relatively big stacked HIGH VOLTAGE and [relatively] HIGH CAPACITANCE (at least for such voltage rating) _C0G_ ceramic capacitor. The interesting thing is that it is sintered into a relatively small almost monolithic block that can be installed two ways. Earlier such stacked capacitors were made by soldering several separate caps to flat bus bar like leads with a high temperature solder. That was adding inductance and didn't allow the "Low Loss" mounting as it is shown in the datasheet for this one. They also were mostly thruhole parts, with several pins on those bus bar leads for soldering into TH pads.
No wonder it is THAT expensive -- it is not a jellybean part that cost a dollar per bucket and you put them all over left and right...
A comparable film capacitor will be bigger and will have significantly poorer ESL and ESR.