If you have ever found a WonderSwan, B$W, Color or Crystal in another country than Japan, it was imported, without the approval of Bandai. and $150 is 2 to 3 times more expensive than what is was in Japan..
Also there is a small error in the desctiption
"ROM: 1KB save EEPROM" mean nothing, there is an internal EEPROM but it''s not used as a save memory for game, it''s only to store some internal information for the console, and the Owner Infos
Also, the Media is proprietary ROM, that''s true, but the "small amount of EEPROM for game save (max 16MB)" is eaither badly written, or just false.
There are two type of possible save method on the WonderSwan, SRAM and EEPROM (like early GBA game in fact), the EEPROM capability have a limit of 16KB (maximum of 13 bit of Address with 16bit data) and have the ability to address 256 * 64KB of SRAM so 16MB in this case.)