Originally Posted by Janh

Yes they can, an publisher can sell his spots flatfee for the price he want, and an advertiser can choose which countries he wanna buy

Besides that he can also buy an spot on CPM base with his wanted countries and browserlanguages, CPM is an bidding system

It is true that mostly huge spots are sold but if an advertiser see trough RON that an site is sending good convertable traffic then he gonna buy it as Flatfee or CPM as well