When working with PPC, it's normal to be running multiple adverts with different keywords.
We all check that our adverts are generating more revenue than they cost to run (or at least, we should all check that!) but have you ever looked at how profitable a particular advert is? Have you ever compared advertising campaigns to each other to see how profitable they are side by side?
ProTip: Compare the "pound for pound" profitability of every campaign and experiment with increasing the budget of the most effective campaigns.