It depends upon which machine it is, condition, and which cabinet it is in.
If it's an ornate parlor cabinet with a red-eye machine in beautiful condition, I will pay a LOT. Well, a lot for me - I expect that when I find "my" red-eye, I will pay through the nose for it.
If it's a 27/127, a 15 or a 66 with ordinary decals and cabinet, I probably wouldn't give it more than a glance.
I'd be more interested in a 128 with La Vincedora decals or in a Singer treadle cabinet.
If it's a 115 with "Tiffany" decals, even more interested.