The Z48(HA) & Z49(BK) and the SW02 are the same switch but the SW02 has "chunky" styling.
As for the price difference. I have no answer but I have some theory:
Z48 & Z49 produced in larger numbers specifically has accessories and are machined from thinner bar stock in an simple style (to machine).
The SW02 is produced specifically for WeaponLights and is aggressively styled requiring thicker bar stock and more metal to be removed in a more complicated process. So making excess to sell as accessories would be more difficult.