I'm guessing the former since $.75 is more inline with other advertisers and a lot of publishers have FastClick set on automatic approval.
I think their ROI was doing ok. In a previous board, one poster mentioned that their content system made the ads more like a site buy instead of a network one, so CPM's should be higher. In a comparison I do with ppc's from Searchfeed, I find the Google content ads only pay me about 1/5 as much and Google gets a lot higher CPC.
All I know for certain is Google got about 22k impressions from at $1 CPM and they ain't getting none at $.75 CPM. Google fans, though, don't worry - I do pay them several thousand/month for clicks to other sites, so I'm pretty sure they won't go bankrupt.