What I can see working out is google setting some kind of conversion:cost metric. ie. if you average 1 action per 1,000 displays pay $10/action; if you average 1 action per 100,000 displays pay $500. It will be a challenge determining the initial conversion ratio. But by common logic - it might take 10,000 clicks for someone to buy a Merc online and Merc won't mind paying Goog $500 for it. Problem arises when a $40 product takes 2000 displays to get a sale.
Well Google can always put unproven sites on the backburner, sending them very little traffic. 10,000 clicks to sell a Merc is a good point, though, it would take forever. Maybe they could do a backburner system but you can pay to jump the queue? Almost defeats the purpose.
What I can see working out is google setting some kind of conversion:cost metric. ie. if you average 1 action per 1,000 displays pay $10/action; if you average 1 action per 100,000 displays pay $500. It will be a challenge determining the initial conversion ratio. But by common logic - it might take 10,000 clicks for someone to buy a Merc online and Merc won't mind paying Goog $500 for it. Problem arises when a $40 product takes 2000 displays to get a sale.
Lots of setting standards, way I see it.