I consider that a quite low price for a fully working one with, what looks like extremely nice condition outside.
Even so, remember Marktplaats is not E-bay. People often bid like crazy and then never show up to buy your stuff... Best way is usually calling/mailing directly.
That monitor can be fixed in 1 second: turn down the screen pot on the HV, and you will have a great picture !!!
It does need the original joystick and a new CPO, but otherwise I wouldn't restore a thing on that one !