C=65 had a built in 3.5" disk drive, high-resolution graphics and CPU at 3.54MHz (C=64 ran at 1MHz) with 128kB of memory (expandable to 1MB) - and most importantly, a C=64 mode, allowing the computer to run C=64's massive software and game selection.
Company managed to build appx. 50 - 200 prototype units, but nothing more. After Commodore went bankrupt in 1994, its assets were liquidated and the prototypes were sold all across the world.
Now, there's one of those prototypes on sale at eBay. Currently the price is appx $3'300 (appx €3'000), but as there's 6 days left in auction, it is highly likely to reach much, much higher levels. In the past, Commodore 65 units have been sold within $15'000 - $20'000 range.
The unit on sale has one major nag: it is missing the VIC-III graphics chip, so the buyer needs to get the gfx chip from other sources in order to actually get the device working, too.
So, if you had your payday and somehow still don't own C=65 in your computer collection, this might be the right time to fix that.