Hi
I cannot say what you should pay but I have sold one in pink in the last year . I would think if you pay between £150 and £200 it would be OK . Less than £150 you may have a bargin . If your buying for you self and not planning to sell then if you pay a bit more I do not see a problem with that.
I am sure I can remember a few years ago that these may have made up to £400 or over in excellent condition but as with lots of glass do not fetch as much now .
Also remember they do not come up for sale that often in excellent condition and I feel they do not command as big as price as some of the rarer Walther pieces.
Roy