2012: 1 million desktop clicks at $1 each + 100,000 mobile clicks at 10 cents each = $1,010,000 total cash, or 0.918 dollars per click, overall.

2013: 1.5 million desktop clicks at $1.10 each + 2 million mobile click at 20 cents each = $2,050,000 total cash, or 0.586 dollars per click.

Overall clicks went up. Mobile clicks went up. Desktop clicks went up. Overall cash went up. Mobile cost per click went up. Desktop cost per click went up. Everything's great!

Except if you're just looking at overall cost per click, it looks terrible.