I think the most expensive machine I ever bought (with my own money)
was a VAX-11/725 in 1986. $4000. I did it, in part because DEC was
eliminating free license transferrals with after-market hardware
sales. It looked like my cheapest option to have my own VAX, and for
a time, it was.
https://books.google.com/books?id=nI091j0HhhwC&lpg=PA7&ots=qK0LibWv…
If only I had a good option (i.e., under $500, and preferably under
$300) for a disk for that thing that isn't the RC25. :-P
Runner-up is probably an Amiga 3000 purchased at the launch for full
price (minus a trade-in discount on an old A1000).
-ethan