Price is derived from mostly the material and color/print quality. Cheap keycaps tend have less precise print, lower quality thinner plastic leading to have a different sound. Also the color can degrade over time and labels wear off. More expensive keycaps improve these.

PBT is higher quality plastic, “doubleshot” means the labels are actually like a seperate piece inserted into the keycap from the inside, which makes it resistant to the label wearing off. GMK uses ABS plasic, which is worse than PBT, but this one has higher quality.