Amazon has the 36-Count BIC Ecolutions Fine Permanent Markers (4 Assorted Colors, Fine Bullet Tip; ‎PMER36-AST) on sale for $9.90 - 5% off with Subscribe & Save (can cancel anytime) = $9.41 with free shipping on $35+ or with Prime. Roughly 26 cents per marker. 

• Colors include: blue, green, black and red.