At a time when e-mail and many other forms of electronic communication are essentially free, wireless carriers are still charging as much as 20 cents to send a text message to a phone, and another 20 cents to receive it.

Paying so much to transmit a handful of words is starting to look as antiquated as buying stamps.

There are now a growing number of ways to bypass text-message charges using an Internet connection — much as Skype allows people to make calls without relying on a traditional telephone line. If these services catch on in a big way, analysts say, they could take a big bite out of the profits that text messages generate for wireless carriers.

On Wednesday, Apple plans to introduce a new service called iMessage, which could quickly become the biggest fish in this pond. The service lets iPhone owners send messages with text, photos and video to other iPhone owners over a Wi-Fi or cellular data connection. The service, part of an update to Apple’s iOS mobile operating system, will automatically handle messages sent between iPhone, iPad and iPod Touch users who have upgraded to the latest software.

“There’s a huge amount at stake here,” said Craig Moffett, an analyst at Sanford C. Bernstein, who covers the telecommunications industry. “They are undermining the core business model for an industry that makes most of its money from services that are high priced and low bandwidth, like texting.”