A single price increase, in fact, could add more than $1 billion to the U.S. healthcare system's drug bill this year, one analyst figures: AbbVie's 9.7% hike on its megablockbuster Humira.

Wells Fargo's David Maris and his team dug into Medi-Span Price Rx data for the period from Dec. 15 to Jan. 3 and found the stickers for dozens of pharma's big-selling drugs grew during that time. None of the companies they investigated implemented a price hike higher than 9.9%, Maris wrote in a note on Thursday. 

Meanwhile, Pfizer raised the prices of 20 drugs by 9.44%, according to the analyst, including for Viagra, Pristiq, Lipitor, Zoloft and Chantix. Four of those—Viagra, Lipitor, Zoloft and Pristiq—are now available as generics. Chantix is set to lose patent protection in 2020.

"It is important to note, the list price in January 2018 remains unchanged for the majority of our medicines," Pfizer's spokesperson said via email. "In addition, for Pfizer’s U.S. Biopharma business, as of the third quarter of 2017, the weighted average net selling price increase year to date is 3%." 

In specialty pharma, Maris and his team found 75 price hikes from Allergan on Jan. 1—far greater than the 18 that was reported early this week—with the majority coming in at 9.5%. A company representative said on Tuesday that the "price increases are consistent with Allergan’s Social Contract with Patients—the average list price increase is consistent with our single-digit commitment, and this will be the only price increase taken on these brands in 2018, again, consistent with our commitment."

Mylan raised prices on 24 drugs but lowered prices on 11 as competitive pressures take a toll on its generics business. Sanofi's only price hike above the medical rate of inflation—5.4% for 2017—was on over-the-counter Dulcolax. Last year, the company committed to limiting price hikes to the medical rate of inflation for its prescription offerings.

Altogether, the data add to the evidence that many execs in pharma are living by Allergan CEO Brent Saunders' "social contract" pledge, taken back in 2016 when the industry was under fire for its pricing. At the time, he said his company will take price hikes only once a year and at single digits, adding that the industry should police itself on pricing or risk regulatory reform.  

But the data also demonstrate that the price-hiking strategy extends beyond a few small drugmakers and their controversial increases that have attracted so many headlines in recent years. While the 5,000% increase for Turing's Daraprim back in 2015 was enough to generate outrage and draw attention to the subject, that price hike's effect on healthcare budgets pales in comparison to the dozens of routine hikes taken each year by large pharmas. Those smaller hikes add up significantly over time. Consider the long-term effect on Humira's price, which has more than doubled in 5 years. It's now the bestselling drug in the world on track to pull in $20 billion or more worldwide. 

In response to that criticism, many drugmakers have said discovering new, effective therapies isn't cheap and that millions of patients benefit every year from their products, some who have no other options.