Comcast has announced a holiday cable modem rate increase that will raise the cost of renting a modem from $8 to $10 a month.

At least 90 percent of Comcast customers reportedly still lease cable modems from the company, delivering a staggering $275-300 million in extra revenue every quarter.

The average modem or gateway offered by Comcast reportedly costs the company an average of $40. At that price, Comcast will earn back its investment in just four months, after which Comcast can book the rest as almost pure profit.

“We continue to make investments in our network and technology to give customers more for their money,” said a statement provided by Comcast. “Last year, we made our 12th speed increase in 13 years, offered the fastest outdoor Wi-Fi hotspots as well as the fastest indoor Wi-Fi connection speeds on our latest and greatest advanced wireless gateways, plus we are at nearly 8 million total Xfinity Wi-Fi hotspots. As a result, we periodically need to adjust prices due to increases we incur in rolling out these new technologies.”

Most Comcast customers are unaware they can buy their own cable modem equipment and avoid the rental fees altogether. Comcast maintains a list of compatible modems on its website, but the overwhelming majority of its customers still pay to lease the equipment.

In December, Time Warner Cable announced a general cable modem rental fee increase from $6 to $8 a month, effective this month.

Comcast’s modem rate increase will be gradually introduced across its service footprint, starting in Boston, Salt Lake City and across Connecticut.