Little much for the Cobra, but from a dealership I would expect no less. However, it's hard to find these cars clean with less than 100k these days. If I could afford it I'd go for it.
Don't expect more than $2,000 trade in value for your car. And, if they don't wholesale it due to the mileage, don't be surprised to see it for sale the following week with a big green $5500 on the windshield. It's just how it works. They probably bought the Cobra on trade for $4-$5k. Again, it's just how it works.
As far as the odometer roll back, with it only being ~5,000 miles difference, I wouldn't read too much into it. That could very easily be someone fat-fingering paperwork at the DMV when the car was re-titled.