VWGigalow via eBay offers the MicroTouch Max All-In-One Personal Hair Trimmer for $7.86 with free shipping. (Walmart and AnyMall via Amazon have it for about the same price.) That's the lowest price we could find by $3. It includes two comb attachments and requires one AAA battery (included).

Update: Most of the merchants mentioned have increased in price, but AnyMall via Amazon still offers it for $7.68 with free shipping for Prime members.