Vintage Guitar Price Guide says that the amp-in-a-case models should fetch $450 to $900 depending on which models. Funny thing, they don't even mention the most desirable model, the 1457. Sometimes I have to wonder if these price guide people have ulterior motives.
I can tell you I bought mine for $400 locally through Craigslist. I talked him down from $450 because there was no footswitch, original cords, the pre-amp tubes needed to be replaced, and the headstock had the tuner wing busted and repaired. This is the 3rd of these kinds of guitars (with the "paddle" headstock of the 1448, 1457) that I've seen over the last 10 years that had a busted headstock just like this. I'm not sure what kind of wood is used, but the holes for the tuners must be a weak spot on the neck and they tend to break off right along the holes... almost like a perforated stamp. My headstock was repaired by re-gluing the wing with 3 screws through the side into the "meat" of the headstock. I probably would have done a less "auto shop" and a little more elegant fix but alas it is what it is and it does the job.
I'm seeing people on eBay TRYING to get $800 for the 1457 but people just aren't buying them for that price.
The folks trying to get $800 for the lesser models like the 1448 I feel even more sorry for. They problem bought them for the maximum price to begin with.
The only way you can get some value from the amp-in-the-case model is if you've had it since you were a kid or can nab one for super cheap. The peak demand for these Silvertones is over, if you ask me.
But then again, Christmas is coming up...
Regarding actual playing/ownership value... they're fun. Luckily mine has excellent action. I have a Danelectro U2 reissue and it basically sounds very similar. I mean, they're the same pickup, even the same distance apart practically, and probably the same body cavity architecture (even though the shape is different). The Silvertone does sound a bit more twangy with less sustain. Definitely a more vintage sound, more punchy.
The amp itself sounds kind of muddy, even with a sweet Amperex 12AX7 in position 1. The tremolo sounds good. You don't get tremolo with the 1448. Also, the 1448 is a 6" speaker while the 1457 is an 8" if I'm not mistaken.