There is a yahoo group called Sew Its for Sale. You do have to "apply" for membership, basic info given to group moderator. Members can (and do!) list everything from machines to patterns to notions... Anything sewing related. If you have the willpower to watch for one for a bit, and are willing to purchase one less than brand new, you might get a good deal.
You can also put an "in search of" listing. For example, you could list the Go! on its own, or with dies, or only for those dies that appeal to you.
Or of course there are the looking for/for sale listings here, too!