B&H Photo-Video offers the EnGenius Gigabit PoE Injector for EAP900H, EAP1750H, and ECB1750 Access Points, model no. EPE-4818G, for $29.99 with free shipping. (NextWarehouse charges the same.) This device supplies power and transmits data to Power over Ethernet (PoE)-capable access points. That's the lowest total price we could find by $4, outside of the mention below.
A close price: NothingButSavings offers this for $30.11 with free shipping.