Does the machine look like it has been looked after? Nice and clean, no dints in the way covers? Don't worry too much about paint flaking off because that happens due to coolant. No gouges in the table?
To buy the quivalent new would be three times that price, but you would get faster rapids, a faster spindle and an LCD display.
That price does seem okay. Of course you can get unlucky but my experience with Haas machines has been pretty good. I have 25 of them and the oldest is a 1995 HL1 which needed repairs to the X axis drive in 1999 and to the Z axis in 2008 with nothing in between.
Naturally you will offer ten percent (maybe even fifteen percent) below the asking price and have nice shiny dollar bills to wave under their nose to encourage them to take the offer.