Dueling Headlines

In referring to exactly the same event, the International Herald Tribune (using an NYT story), runs the following headline:

"Tens of thousands march in Washington"

While Yahoo, running an AP wire report, gives us:

"Some 500,000 Rally for Abortion Rights"

Who's shilling for whom here? In the IHT/NYT article, the lowest estimated number of marchers is 250,000 (that's CNN's low-balled bid).

So, is it tens or hundreds of thousands? You could argue that both headlines are, technically, correct. The former, however, is correct in the same way that the following statements are correct:

It's hundreds of miles to Australia from here.
Bill Gates is worth thousands of dollars.
The Vietnam War memorial displays names of the dozens of American soldiers killed in that war.

See?