Cost per Sale for AdWords?

Google AdWords is maybe the best trackable media; you can track every single click, conversion and Euro.
You can perfectly link Google AdWords and Google Analytics and get data beyond the click as well.
In certain cases AdWords falls victim to this transparency.
Companies are often too strict and Google AdWords is put under the microscope because it is so trackable. If the cost of conversion is higher than what they expected it seems like "We are losing money with AdWords". And often the conclusion might be: "Oh Google AdWords is too expensive lets reduce the budget or stop it!"

This is not quite the case.
What is the cost of conversion of radio, magazine, TV, cinema, outdoor etc?
"Oh but that's branding, Adwords is not for branding it is only for sales/driving ROI."

What better branding is there than bringing a potential client who is interested in your products to your website and let him experience the full effect of your website branding, with logos, banners, messages etc?

My advice on this is:

• Don't be too strict with the conversion rate/cost with AdWords if you are not with other media
• Use attribution models to see if keyword groups which don't lead to sales drive sales indirectly (last click vs first click e.g.)
• AdWords can be a strong brand awareness driver as it brings your target audience to your website which is highly branded. 
• ROPO (Research Online Purchase Offline) will definitely occur in most industries. AdWords will increase Offline sales but it will be hard to track 
• AdWords has a positive effect on organic searches

CTR goals, the higher the better?

Let's say you are running a PPC campaign on Google AdWords and you are wondering what CTR is good...

Google AdWords Account-Campaign Level Screenshot 

What is a CTR?
The Click-Through-Rate (CTR) shows what percentage of the people who see your ad actually click on it.
The CTR is an average and can be found on different levels, Account level, Campaign level, Adgroup level and Keyword level. It is a good indicator of how relevant your ads are to your keyword.

Why should I optimise my Google AdWords Campaigns for CTR?
The CTR is an important factor in the Google Quality Score. Google rewards relevant ads by giving them a higher Quality Score. A higher Quality Score might mean that you pay less per click for your ads, or alternatively your ads get a higher ranking for the same cost per click.

Search CTR vs Display CTR
First of all one should distinguish between GDN (Google Display Network-formerly called Google Content Network), and Search. In Google a Search CTR of about 2% and above is regarded as good and for the GDN, 0.10% is regarded as normal. Anything less than these values should be investigated further.

Brand CTR vs Generic CTR
It is also important to distinguish between brand terms (e.g. Adidas) and generic terms (e.g. runners). A brand campaign might have typically 20%-30% CTR. Non-Brand campaigns (Generic) should have 2% at least as stated above. And by the way, if you haven't separated brand vs generic keywords into different campaigns then please do. It is not easy to assess and manage a mixed campaign.

CTR and Traffic
When I was working in Google, one inexperienced industry sales manager said: "I don't regard any CTR less than 4% successful!"
Hmm, ok... let's analyse this further.
Through optimisations you can influence the CTR. The CTR is in negative correlation with traffic. Below you see a very simple graph showing this correlation.

The more specific you become, the higher the CTR, but you will sacrifice traffic on the other hand.
Well, through optimisations you could even achieve an average CTR of 15% on generic terms, but traffic would suffer. So it is not advisable to set rigid CTR goals. Striving for a too high CTR is not advisable.