Because it's relabled under Meguiars and Megs offers a lifetime warranty on the G100. To some people, the warranty is worth the extra money....to some it's not.
I've had my G-100 for over 9 months now and it's been used at least 5 times per week for hours. I've not one single problem at all. The lifetime warranty is still conforting though.
if your a pro. detailer i think the warranty is good but if not,id get the 7336/7424.thats what i have because the extra warranty wasnt worth the extra $100 IMO.