Trick is, nobody is buying ads at the moment because nobody is spending on advertised products. So demand is way down, which means the value of the ads is also

Trick is, nobody is buying ads at the moment because nobody is spending on advertised products. So demand is way down, which means the value of the ads is also way down. By donating half a billion dollars worth of ads at today's rate, they generate half a billion dollars worth of demand and keep the price pumped up. If the numbers work out the right way, they might even be turning a profit by giving ads away.