Amazon offers its Prime members the Star Wars Rebels Command Epic Assault Set, model no. A8957, for $6.92 with free shipping. (Non-members can spend $35 or more to dodge the $6.32 shipping fee.) That's the lowest total price we could find by $2, although most stores charge $16 or more. It includes 22 figures and vehicles.
Orders placed via Prime by December 22 are guaranteed to arrive in time for Christmas. (The deadline for standard shipping is December 19.)