Some traffic sources are able to pass cost per click in real time, usually with a token like {cost}.
In such cases, you would add this as a token in the cost / CPE field in traffic source settings:
However, some traffic sources are able to pass the CPM bid, not cost per click, which for sources like pops/redirects will be approximately 1000x the cost per click value.
In these cases, you can prepend cpm_ before the cost/bid token, like so:
In a live URL, this would append ...&c=cpm_12.34 to a URL. Our edge will detect the cpm_ prefix and calculate the incoming cost as 12.34 / 1000 = 0.01234 as the cost per click
If you find a traffic source in our templates where the cost token is present but should have this modifier added, please let us know.