I got lucky and got a working SC-55 Mark 1 (some front panel controls are a bit sticky, but I don't care for my use case) for 80$ at a local (Montreal) pawn shop last winter . Ironically, they had had it for months before anyone showed any interest and actually knocked 20$ of the 100$ asking price to entice me .
This pawn shop, like several other in my array, has a searchable inventory on its web site, so anyone in the area could have found and bought it months before me . I actually stumbled upon it by sheer luck ( I was looking for something else and decided to check for Roland/Edirol gear for kicks).
Anyway, I admit I was really lucky, but searching online locally is never a bad idea, IMHO.
Case in point, around the same timeI found online and purchased an RA-50 for under 100$ from a guy who lives maybe 10km away .
My first SC-88VL about 4 years ago,AFAICR, was a 40$ purchase. I found it lovally as well thanks to an add on Kijiji .
All $ amounts mentioned are Canadian funds .
Good luck!
EDIT : This strategy is more likely to be effective in a densely populated urban area, it goes practically without saying .