Yes, you can set a separate CPC for Pubfeed placement within the same campaign.

When you go through the campaign set up flow in the Linkby platform and have selected Linkby Pubfeed as a placement, there's a tick box to Use different CPC for Pubfeed. Once this is selected, you will be able to input the desired CPC amount, which will override the normal campaign CPC when your content is delivered via Pubfeed.