I'm amazed more people don't understand why this happens, especially Tom's.
Youtube ad revenue is roughly $1500 - $2000 per million views, and anybody and there mom can get in on that. The value depends on the ad campaigns being run, but you can safely bet there are high paying ad campaigns during the holidays. Bottom line, views = money, and these guys very likely know that. It's a gamble, but if you get a viral video (which sites like this contribute to, so obviously it's working), you'll make back the $400, and a few grand more if you're lucky.
I'm shocked Tom's writers don't realize this, as the source of income is nearly identical to how all of the staff at Tom's is paid, and how websites exist as a business.