If it was a gift for someone or it had sentimental value AND I was afraid someone would snatch it up before I could save enough money then I would make the purchase on credit. I'd make sacrifices to get it paid off quickly though.
I'm not a fan of credit cards......at all......but I would seriously think on that one. Chances are I would, but it would really have to be a one of a kind.
I would not use my credit card to buy an antique unless I could pay it off immediately and I was using the card simply for added protections. The interest just isn't worth it. Another great item will come along down the road.
If it's way outside of your budget, then I wouldn't get it. Just my opinion, but if a luxury - even a really cool one that's hard to get - is way outside of your budget, then it's not worth it. However, there are other factors to consider as well, such as sentimental value.
I would probably go for it. Things like that don't always come around very often. I would check and make sure that's the case though. Sometimes, things are more common than you think. I'd also check prices online and see if I could find it for less and/or compare prices.
Kingfish, let me ask you this: Do you want the radio because it's awesome and you want to have it for yourself? Are you going to use it? If yes, then do it. It doesn't matter if the value depreciates.