MZ-S is the top AF camera by Pentax, it's still selling for very good price on second hand market. A brand new black one can easily get over $600USD while a used one for $400USD or more. The silver one is not easy to come by, which also selling for slightly higher price. It's much better built than cameras like Z1, MZ3, MZ5 and etc. It also has some fancy features like change films on the go (you don't need to finish one roll when you wanna change another one), EXIF in print, wireless flash, 19 custom functions ...
You can see several black ones sold on eBay every month, but only one silver one in several years. That's why I want this one quite badly, especially a good condition one