Guitar Center offers the Hohner Roadhouse Blues Harmonicas 5-Pack for $16.99 with free shipping. Outside of the seller below, that's the lowest price we could find by $3. It includes a custom case and harmonicas in keys of G, A, C, D, and E. Deal ends May 10.
Don't need it soon? Amazon offers it for $15.99 with free shipping for Prime members. However, it's temporarily out of stock, and a ship date is unknown. (You can still order at this price, and it will be shipped once it's available.)