SBP Center Line Wheels

No offense meant but.... i think you have 15x4 and 15x8 1/2 centerline autodrags. You can see in your second picture that the tires mounted are 185/65x15.
Wheels are measured by where the bead of the tire sits. So a 8" wide wheel might measure nine inches outside edge to outside edge. The same applies to the rim diameter, a sixteen inch measurement across the face of the rim is always a fifteen inch wheel.
That said , in my opinion, your price is very fair, considering the sbp centerlines arent being made any more, and the current prices of new autodrags has skyrocketed.
To be fair to your buyer though, you must include the center caps, they are smaller than standard, and hard to get.