[rcar]

STL files are the 3D models that you put into your slicer of choice (which converts the project into the thin layers that the printer will gradually put down).

There's a dozen things to print in the zip. I sliced 3-4 of them, and none seemed particularly heavy. Something like $0.50 of filament each for what I pay for PLA, which would put the whole thing at ~$6 of material. Perhaps the cost is being driven by some sort of print-on-demand costs?

FWIW, you could also buy an Ender 3 for ~$200, and $140 buys a lot of filament, so you could get into the 3D printing hobby for less than the quoted cost.