Amazon offers Prime members the Barbie Fashionistas Doll 4-Pack for $19.52 with free shipping. (Non-members can get free shipping with orders of $35 or more; otherwise, it adds $6.62.) That's the lowest total price we could find by $15. It includes Barbie, Teresa, Raquelle and Nikki dolls.
Orders placed via Prime by December 22 are guaranteed to arrive in time for Christmas. (The deadline for standard shipping is today, December 19.)