I bought a very lightly used Bernina 770qe (without the embroidery unit) from an individual for $3,050 off of EBay. I contacted the Seller before the auction ended to get their agreement, if I won the auction, to allow me time to have the machine inspected at my local Bernina dealer, and that they would pay for any needed repairs.
No repairs were needed and it has been great! I had no hope of ever affording a new machine (senior living on Social Security), so I took a chance, knowing EBay would have a record of our purchase agreement. I sold my other two sewing machines to help fund the purchase, too.
Good luck on your search!