It's also one of the only Sonic titles to not have been re-released in some form or another, which makes it a very rare find on the second-hand market – especially with all of its original paperwork and manuals.
That's why a recent listing on the Japanese marketplace Mercari is so interesting. A copy has been listed for sale at $3000 USD, and includes the ROM board, motherboard, original trackball, art assets and service manual.
It would appear to from the collection of a private collector, who, in the listing's description, claims to have done some repairs on it after the suicide battery died. They have also fashioned a custom board to connect the trackball to the motherboard.
"Board labelled 834-6180 is a homemade one," says the seller. "It is necessary for connecting the trackball to the motherboard. When I purchased the ROM board, IC17 and IC19 had dead batteries, rendering the game unplayable. I repaired it myself and removed the need for the batteries. Let me know if you require the original IC and battery."
This is an incredibly rare find; most copies of SegaSonic are conversions, and the game rarely appears for sale with all of its original assets.