Walmart offers the Hohner Blue Ice Harmonica 3-Pack, model no. BIP, for $9.48. (Amazon and Musician's Friend have it for the same price.) Opt for in-store pickup to avoid the $4.97 shipping charge. That's the lowest price we could find by $4. It includes a carrying case and plays in the keys of C, D, and G.
Update: Note that Amazon is now temporarily out of stock, however it can still be ordered at this price for delivery when available.