You can't just display an ad at any price, even if there are no other ads. There are too many spam ads now, but it used to be quite a bit worse. Setting a minim

You can't just display an ad at any price, even if there are no other ads. There are too many spam ads now, but it used to be quite a bit worse. Setting a minimum price sets the bar high enough to make it not worth the cost to spam. It's gotta be a juggling act for Google to keep prices within reach of legitimate advertisers while keeping out the riffraff. The only other solution is to manually approve all ads before they go live.