[Arran]

 Paying someone to restore a radio for you is usually a loser in terms of resale value, a lot depends on what you paid for the set to begin with, sometimes even if it was free it still ends up being a loser. Most of us buy a radio because we like the set or because we find it interesting for one reason or another, not for resale.
 From what I can tell this set looks like a typical late 1950s piano key German set, except that it is Dutch make and not a German one even if it was aimed at the German/Austrian markets. I see asking prices for some German sets in the $200-$300 range on fleabay if they are working top end models of certain makes like a Blaupunkt, but then again those are buy it now prices and if they don't take offers they seldom sell. It's basically worth whatever someone wants to pay for it, there is really no guide to what things are worth unless there are lots of other examples to go by, and what you have invested in it really has no bearing on what it's worth to someone else. 
Regards
Arran