The price is insane.
Check their FAQ:
19. Why are Signature Plastics’ DCS and DSA style keycaps so thin?
As offshore competition for keycaps began to grow in the 1980’s, it became necessary to reduce costs as much as possible to remain competitive. As a result, subsequent families of keycaps, like the DCS and DSA families, were designed to use less material.
Is it still nessesary to reduce cost of raw materials, if we pay premium prices...