I'm not really sure what cost $300 million about this ad campaign. Let's do the math:

Seinfeld's salary: $10 million, although that's rather steep considering he's done absolutely nothing for the last decade.

Production: $500,000, have you seen these ads? What about them possibly costs money to shoot? Did they have to rent the entire city that this house was in to be allowed to shoot there?

Distribution: $100 million, on the steep side.  I've seen a few of these spots on TV here and there, but mostly they're spread around the internet like wildfire by themselves. Oh also, no network is going to air a five-minute long commerical.

My best guess for the other $289,500,000? A secret second ad campaign that actually is about you know, selling Windows products.