NRG Stadium in Houston.

Super Bowl LI takes places in Houston. Image source: Visit Houston.

While viewership is down for television overall, the Super Bowl remains a ratings monster that commands staggeringly high ad prices. Last year's game, where the Denver Broncos beat the Carolina Panthers, drew 111.9 million viewers, according to Nielsen. That's down fractionally from the year before, but it's good enough to be No. 2 of all time. To put those numbers in perspective, the top-rated regularly scheduled broadcast network shows that are not football games are lucky to get 15 million viewers.

In addition to having a huge audience, the Super Bowl commands high ad rates because, to many of the people watching, its commercials are as important as the game. (Sometimes, they're even more important.) There's no other event that airs on American television where people discuss, dissect, and share every ad. Super Bowl commercials receive an astounding amount of exposure outside of the game, which gives the networks that air them tremendous ad pricing power.

That's why prices have risen from $37,500 for a 30-second ad during Super Bowl I to $5 million per 30 seconds for this year's Super Bowl LI, which takes place February 5, 2017. The big game rotates between the current NFL major package-rights holders Comcast (CMCSA -0.36%) (NBC), FOX (FOX), and CBS (PARA 1.44%), but no matter which network airs the game, the prices have steadily gotten higher -- although they haven't increased every year -- as you see on the chart below.

Average price of a 30-Second ad for Super Bowl I to 50

Super BowlCost of 30-Second Ad Super BowlCost of 30-Second Ad
I 37500/$42,500*   XXVI $850,000
II $54,500   XXVII $850,000
III $55,000   XXVIII $900,000
IV $78,200   XXVIX $1.15 million
V $72,500   XXX $1.085 million
VI $86,100   XXXI $1.2 million
VII $88,100   XXXII $1.29 million
VIII $103,500   XXXIII $1.6 million
IX $107,000   XXXIV $2.1 million
X $110,000   XXXV $2.2 million
XI $125,000   XXXVI $2.2 million
XII $162,300   XXXVII $2.2 million
XIII $185,000   XXXVIII $2.3 million
XIV $222,000   XXXIX $2.4 million
XV $275,000   XL $2.5 million
XVI $324,300   XLI $2.38 million
XVII $400,000   XLII $2.69 million
XVIII $368,200   XLIII $2.99 million
XIX $525,000   XLIV $2.95 million
XX $550,000   XLV $3.1 million
XXI $600,000   XLVI $3.5 million
XXII $645,000   XLVII $3.8 million
XXIII $675,000   XLVIII $4 million
XXIV $700,400   XLIX $4.5 million
XXV $800,000   50 $5 million

Data Source: Nielsen. Media Research.
*Super Bowl I aired on both NBC and CBS.

Why are Super Bowl ads getting even more expensive?

The fact that the television world has gotten so splintered has helped CBS, NBC, and FOX increase prices dramatically over the last few years. Final numbers are not in for this year's game, but the average was expected to move higher than last year.

Getting access to the Super Bowl once every three years is a major reason why FOX, CBS, and NBC pay billions collectively for NFL rights. In addition to raking in cash by selling ads, the networks also get key exposure for their own shows and a huge post-game audience to either promote an existing, or new, program.

There's simply no other way to reach that many people all at once, and that allows the networks to pretty much name their prices. In addition, the added exposure for Super Bowl ads has only increased since the internet has become such a powerful force. There might be a ceiling for the cost of a 30-second Super Bowl spot, but numbers should keep going higher as long as the National Football League can keep delivering ratings that no other programs approach.