75 years ago, in 1941, the first commercial ever aired on TV. It was aired just before a Brooklyn Dodgers vs. Philadelphia Phillis baseball game.
The ad cost Bulova 9 bucks (approximately 150$ if you consider inflation - http://www.usinflationcalculator.com)

I really love the ad!

 

As for the source, I found it in a Swiss newspaper. I can post the link if you're interested.