Google ads cost whatever your fellow competitors are willing to pay for the same keyword as you are bidding for.

We have clients who spend no more than £5 a day and others who spend no less than £50 a day. Part of a professional service is to maximise what you are prepared to pay by tweaking the multitude of ever changing settings and not accepting blindly the defaults and recommendations you are constantly given. Also have in mind what the ads are being used for and where you want them to show.