10-Pk 1KG Polymaker 1.75mm Panchroma Matte PLA 3D Printer Filament (Charcoal) $98 + Free S&H

Under $10 a spool for one of the best filament brands. Only charcoal for this price sadly (5 charcoal and 5 white for $104.99 which is a good deal too -- the color option is a bit more) ...