Around 4-4.5k for a good condition stock standard. Anything more would need to be over and above factory specs (aftermarket mods or restored) to warrant a higher asking price.
Watch out for ghosting on the blue kidney shaped inserts in the centre of the playfield.
Shockingly bad pictures on that gumtree listing. Out of 10 pics, 7 are out of focus and 2 sets of identicals.
