£36 is that per day / week / month ? whats the url of the website?
The cost of the keywords is based on several factors, one of the most important factors is "Quality Score"
"The AdWords system calculates a 'Quality Score' for each of your keywords. It looks at a variety of factors to measure how relevant your keyword is to your ad text and to a user's search query. A keyword's Quality Score updates frequently and is closely related to its performance. In general, a high Quality Score means that your keyword will trigger ads in a higher position and at a lower cost-per-click (CPC)."
Id recommend reading through the ad-words documentation, if its a little to dry for you and you want to take advertising seriously you need then do two things. Increase your budget and hire a professional.
Geoff.