In order to lower the price per lead, you need to have a look at your geography and criteria. If you have a very strict geo with few counties and states, you can add new counties, and it will decrease the price. Also, the higher the budget you have, the lower the price per lead is going to be. 

On top of that, if you have many criteria disabled, resulting in fewer leads, it is a good idea to reverse them enabling us to generate more leads for you and lower the price.