The fact that brands are demanding more mobile ad space is a reflection of the fact that more people are using smartphones over computers. An eMarketer study suggested that about 24 percent of time spent in the U.S. consuming media is through mobile devices, compared with just a little over 16 percent for desktop.
Not only are more consumers on mobile, but advertising can be more advanced, Fogel said.
"In 2015, I would actually posit that mobile is now the fully featured version of the Internet, and PCs are the limited version," he said. "What mobile can do now — geolocation, deep linking, iBeacons, payments, sensors, touch ID and activity trackers — makes the PC look quite limited in comparison, as there's only a browser and a keyboard."
Matt Waghorn, director of communication planning for digital agency Huge, said the fact that mobile was outpacing desktop did not surprise him. He pointed out that other worldwide markets suggest that mobile will eclipse tablet, PC and laptop usage. Compared to other countries such as India, China and Brazil, the U.S. lags a bit in mobile adoption.
He said the lack of ad blocking also makes mobile advertising more appealing to brands. Ad blocking capabilities doesn't seem to be as advanced for smartphones, especially when it comes to in-app advertising, he said.
"The rate of growth in mobile and the rate of adoption is only going to escalate," said Waghorn.
But, he pointed out the higher mobile prices may be more applicable to certain ad categories. In his experience, display advertising such as traditional banner ads tended to go for twice the price on mobile compared to desktop. Other types of ads, like preroll video advertisements that show up before a clip, still came in about equal, he added.
The PubMatic study also found that Apple iOS app advertising was found to be increasing the fastest in price and volume, compared to Android app ads, mobile web ads that show up in browser, and tablet web ads.
"Apple iPhone customers are seen as more valuable," Waghorn said. "They're wealthier and older, where Android users are younger. I would imagine it's an audience play."