Why so much for 1 gallon kit

Was in Phantom ales grabbing some things and tried their Bourbon Porter, Was good so at home went online to order a 1 gallon kit. $15 for a gallon kit when a 5 gallon kit is $46.99 ( the same with most others as well). A Small Batch kit IMO should be 1/5 the cost of a 5 gallon. Why so much