I found one for sale on eBay for $4,500 and free shipping:
http://www.ebay.com/itm/like/1723885...&ul_noapp=true
You may be able to find a price range by searching through patternreview.com . Unfortunately, their reviews are categorized by brand only (Brother), so there are many many pages you would need to scroll through to find all of the reviews for that machine. However, the reviews typically include price paid information, so it could be worth your time. Just on a brief scan, I found this review that says she paid about $3,000 for it (but some time ago):
http://sewing.patternreview.com/Sewi.../Review/1/5168