Price/value depends on how strong the Amiga scene is in your area?
Here in Aus the scene is all but dead, there are loads of old A500's around, so they dont fetch anything, Ive seen them in charity stores for AUD$5-10 with a crapload of disks and bits.
The A600 is virtually an A500 and though much rarer here, they still only fetch pocket change. Even A1200's go for ~AUD$100-200, when sold by "people in the know" to other "people in the know".
My point is, (outside the community) these things are just -really old computers- and not worth anything.