BoJangles,
If it is still in the factory shipping box from Singer 1910, $800 would be discussable.
But, if it has one scratch on it, anywhere, it is only worth as much as you want to pay for the cabinet.
Buy for the cabinet, not the machine, in this case. If the cabinet is absolutely no doubt PERFECT, I would pay $100 to $150 for the whole thing, machine and all.
Oh, and for $150, it had better be my most favorite cabinet style.
If the machine is absolutely PERFECT, I would pay up to $80 for the machine, and it had better have slide plates, bobbins, a lot of accessory feet, etc. Because, there are a lot of nearly perfect machines in cabinets out there for $40-$80 all included.
This is my opinion after only three months of treadle browsing on CL. If I am crazy, well, forgive me.
Aardie.