rather late update:
after showing this thread to the shop, they agreed that they were originally wrong, and I was actually looking at about $700. I am not mad at all, the shop owner is a good drinking buddy of mine.
So on the last oil change, I put in a thicker oil, 15W-40
, and now its virtually leak free
I have have put almost 1000 miles on it since then, and when I checked it today, it was down 1/2 quart. I think this will temporarily fix it enough to sell as-is without feeling completely horrible about it.