I don't know how long Happ has been selling that, but I first saw it on their site a couple weeks ago. One possible reason someone may want to dish out the $$ for this is if they wanted to use the latest/greatest video card in their MAME cab since it requires a VGA card, where the ArcadeVGA is a specialized video card for use with arcade monitors.
Besides, these aren't priced for the average consumers. I have to imagine the target market for this device is OEM's.