Can I change the price per ad-view at any time in my screen?

Yes. But when you change you screen ad-view price, the existing campaigns runing on this screen won't be changed, but since you changed the price, the advertiser will receive an alert with your new price to approve. For example, if an ad is playing on your display for 2 cents per ad-print, and you change your mind and turn it to 5 cents, this ad will stop playing on this particular display, and the advertisers will have to approve this change. 

Refer to this article to understand what we say to the advertiser for the same question.