Toys"R"Us offers the Crayola SuperTips Washable Markers 20-Pack, model no. 58-8106, for $3. Opt for in-store pickup to avoid the $5.99 shipping charge. That's the lowest price we could find by a buck.
Also available is the Crayola Pip-Squeaks Washable Markers 16-Pack, model no. 58-8703, for $3 via in-store pickup. That's also the best deal we could find by $1.