Depending on the amount of screenshots/adds you get per shout, anywhere from $400-$750 24hrs. Reason for my appraisal is, I sell shouts on my 25-30k audience for $40 24hrs. Also know of others selling 4k adds for $100. You're looking at good chunk of change for 24hrs.
Thanks, might open a thread soon for this. I doubt many people would pay $500+ even if their account/site is being blasted in front of 400,000 people so I'll probably aim for mid-400 to low-400 range.