am I crazy?  

Well,
it's entirely possible to safely ship electronics, after all, they're not all made where they are purchased.
But in this case it's all down to how carefully the seller packages it.
Do you have any knowledge of the seller and any past transactions ?

Only than 4 years of active...
Only than 4 years of active selling I know nothing.
He states he can send it safely packed from Holland to Belgium (it's not that far).
What would be fair prices for these vintage audio pieces?

I'm no expert
but it seems a very good price to me !

driving up there ?
Hey bj, I agree with robert. It depends for a large part on the packaging skills of the seller, and a bit of luck with the postal services. I once bought a radio from Germany, and the seller did a fantastic job of packaging it safely. It got here in one piece :o). But I must say, I found it to be one of the more scary transactions. Until it safely arrived, I have been biting my nails. You are better off paying the seller more for shipping a large parcel, so he/ she can make a big package of it with lots of isomo (sorry, don?t know the English word) and other isolating stuff for protection. (Be prepared to pay more for a larger, heavier package with lots of stuffing, I think I paid something like 25 to 35 EUROs). And untimely, yes, there is still a risk involved. So how bad do you want this radio ?
Instead, as the seller is in Holland, can you not ask where he/ she is located and whether you can pick the radio up in person ? If the seller lives close to the Belgium border (and is okay with pick-up), it?s not so far to drive there (sometimes less than 2 hrs). Then you can bring it back on the backseat of your car. You have most control over not- breaking it that way.
Anyway, I sympathise !

Thanks for the sympathy...
Thanks for the sympathy ite!
The seller is a bit to far up located, would spend a lot of petrol.
A bigger package would be an idea.
On the other hand, I'm a bit nerveous that the seller would sell a defect radio (stating otherwise), shipping it, and then plainly stating it probably went broke in transport..
We'll see...
But I really do wanna have the radio 🙂 !

Well, yes, there is always...
Well, yes, there is always that risk.
I actually let the chance slip to buy my radio model earlier, from a website of a vintage dealer in Holland - and purchased the model later on Ebay from a German seller. In the end, the feedback system convinced me: I could see in the feedback that the seller had sold something similar earlier - and had received positive fb for it (so assumedly it arrived unharmed). Additionally, he did have very good overall feedback, so it did not seem like he was taking liberties with the item descriptions. The parcel indeed arrived very well packaged -in a massive oversized box with lots of protective stuffing-, and truthful to the photos and item description, exactly as promised. I chickened out of buying directly from a non-feedback website though. There is no way of telling whether the seller ever had to ship more tricky items, or would play tricks as you describe. You'll have to take a chance with both venues, but you have more information beforehand with Ebay - so the chances you take with Ebay sellers seem smaller (at least to me).
Nonetheless, buying vintage audio equipment is always scary, even if you can test it beforehand. The equipment inevitably comes with mileage on the teller from previous use. And if it has been stored, dust is a big enemy of electronics. Even if you test it before you buy, you only know whether it is broken or not at that time; if it works, you never know beforehand how much life it still has left. However, that time I really wanted that piece and it was not too expensive, so I felt like taking the gamble. (I did not buy the speaker boxes, I later combined it later with new ones). For a more expensive audio piece, I prefer to buy new, with warranty, from a local dealer.
There is no way of making this thing 100% safe, basically. This transaction equals a gamble. It's your call whether this is worth it to you or not. You can minimize your chances:
- Check the seller's reputation if you can, feedback systems are great for that.
- Also, as someone mentioned earlier on another thread, when in doubt about packaging, simply ask the seller how the item would be packaged. If the seller cannot or will not tell you, bad sign. Or if you are told, that there would only be one layer of bubble wrap around the radio, bad sign, that will not keep it safe in transport. OR try to be the one responsible for the transportation, then it's in your own hands.

.
Also ask yourself the questions how you would feel it things went wrong.
Suppose, worst case scenario, the seller does not ship: Can you get your money back through PP ? Alternatively, the seller does ship, but the radio does not function. Would you still like the piece for its shape, as a work of art for this price ? (Or would you only want it if it functions allright ?) If "no" is the correct answer for you, I'd say pass this one up. If you are inclined to answer "yes", try to find out more about the seller's reputation and the packaging. (If either one is bad, pass it up. If you cannot find the info, ??? )
At the end, it's your call whether to buy this one, or wait for another one to come along. And yes, I remember I found it rather stressing to decide what to do .. :o) Hope that you find a decision that feels right to you, whatever way you decide to go !