I offered $3400 as a starting off point a few weeks back and asked about HUO docs (which he does not have) and was told $3800 firm too....looks like there may now be movement on price for anyone that may still be interested.
It's listed on Mr.Pinball today:
Ripley's Beleive It or Not, 2004 Stern: $3700.00
Purchased from original adult (HUO) owner. By far the best RBION for sale. Looks like it was just unpacked. All original except for batteries. Could help move within 50 miles of Balto. MD. for a small fee.
Good luck OP!