The cost to hire an Adwords agency depends on a number of things. For example, if you’re business is local you may want to consider the “local campaigns” in Adwords, which can give your ads a higher place in the SERPs. What also changes the price is the level of experience and expertise of the company you choose, along with how many competitors are bidding on your keywords. If you choose a small company in a competitive market your CPCs will be higher than if you went with a large enterprise in a fairly non-competitive market.