Twenty years ago, 30 seconds of ad time during NBC's "Seinfeld" was the most expensive real estate on TV. But it was still a steal compared to this year's costliest programming, revealing just how much the splintering of TV's audience is changing the math for marketers.

Advertisers paid an average of $575,000 per spot in the sendoff season of "Seinfeld" from 1997 through 1998, according to a contemporary Ad Age report. That's a staggering $876,959 in 2017 dollars—topping everything then and now. This year's most expensive show, "Sunday Night Football," averaged just shy of $700,000 a throw for NBC in upfront negotiations.

But the final season of "Seinfeld" also averaged 22.3 million viewers in advertisers' coveted 18-to-49-year-old target, making it TV's highest rated show. The cost per thousand impressions, or CPM in TV jargon, was $25.80 in 1997 dollars and $39.35 when inflation rates are factored in.

That would be an enormous discount on the per-thousand cost of today's "Sunday Night Football." Through the first four weeks of the new NFL season, "Sunday Night Football" is the top-rated prime-time broadcast program, with an average of 9.28 million viewers 18 to 49. So the target-demo CPM for "SNF" is $75.38, a 92 percent premium over the inflation-adjusted cost of reaching 1,000 such viewers in the final season of "Seinfeld."

That said, marketers don't have the option of traveling through time to buy commercials under 1997 conditions. And when both programs' CPMs are compared to the industry averages in 1997 and 2017, a 30-second spot in "SNF" isn't nearly as dear as an ad that aired in "Seinfeld" two decades ago. The NFL showcase sells at a 76 percent premium to the average prime-time CPM ($42.90), while the cost of reaching 1,000 "Seinfeld" viewers was more than double (+131%) that season's average broadcast CPM ($11.18).

Bragging rights
As was the case in 1997, when NBC offered six of the most expensive broadcast buys—the Must-See TV lineup of "Friends," "Union Square," "Seinfeld," "Veronica's Closet" and "ER" on Thursdays was joined in the top 10 by the Tuesday-night comedy "Frasier"—the Peacock this season boasts an alignment of pricey shows. Along with "SNF," NBC's six-game "Thursday Night Football," its sophomore drama "This Is Us" and the veteran competition series "The Voice" have advertisers digging deep for the privilege of getting their marketing messages out in front of some of TV's biggest audiences.

Looking back at the 1997 data, the most valuable broadcast inventory priced out within a fairly narrow range. "ER," which that season would average just under 20 million members of NBC's target demo, commanded $560,000 per 30-second spot, which works out to a $28.04 CPM … or $42.77 in today's dollars. "Veronica's Closet," which benefited enormously from leading out of the "Seinfeld" swan song, drew 16.3 million adults 18 to 49; given a $400,000 unit cost, the show's CPM was $24.58, which adjusts to $37.49 with inflation. Season four of "Friends" averaged 15.4 members of the demo, while fetching $410,000 per spot and a $26.57 CPM, or $40.52 in current dollars. "Frasier," which reached a relatively paltry 9.91 million adults 18 to 49 (for the sake of comparison, that would make it the No. 1 scripted series of 2017), carried a $275,000 unit cost and a $27.73/$42.29 CPM.

As it happens, the NFL of 20 years ago wasn't the monolithic beast it is now. ABC's "Monday Night Football," which stood as TV's lone prime-time NFL package, was only the seventh highest-rated program of 1997-98, averaging 11.1 million adults 18 to 49. Advertisers buying time in the weekly game paid around $360,000 for each 30-second in-game ad unit, which translates to a $32.32 CPM—$49.29 in today's dollars. (The "Monday Night Football" package, which now airs on ESPN, fetches around $425,000 per :30, good for a $71.86 CPM against an average delivery of 5.91 million adults 25 to 54.)

Another big earner in 1997 was ABC's "Home Improvement," which was the worst value among all top 10 shows with an average CPM of $34.05. Based on an average draw of 10.3 million viewers and an adjusted unit cost of $472,795 a pop, "Home Improvement" commanded a $51.93 CPM in 2017 dollars. Fox's "The X-Files" was the best buy of 20 years ago, scaring up 11.9 million adults at a cost of $275,000. That works out to a $23.07 CPM, which adjusts to $35.19 with inflation.

And while we're doing the media math, it's perhaps of interest to note that 20 years ago, a New York subway token cost $1.50, a sum that in keeping with the occult principles that hold sway over the local economy, was roughly what you'd pay for a decent slice of pizza at the time. And for the cost of 17 one-way trips underground or as many triangular servings of dough, sauce and cheese, a savvy advertiser could reach 1,000 demographically relevant viewers in "Seinfeld."