The analyst firm said that building and operating a personalised website using cookies to target each consumer can cost four times more than a comparable standard dynamic site.
Its research showed that only 14% of consumers would buy more often from online stores that included personalised offers or recommendations. This is in contrast to the majority of consumers, who stated that basic improvements, such as faster loading pages and better navigation, would be greater incentives.
"Our industry has always assumed a personalised website was a better one, but our research has shown this is not the case," said Matthew Berk, research director at Jupiter Research. "Most personal websites fail to deliver real business benefits."
A separate report from Forrester Research painted a brighter picture. The analyst firm said online retailers should follow the example of e-commerce firms such as Amazon.com and continue to invest in personal technology.
Although online retailers invested heavily in technology during the dotcom boom, many have had to cut their spending in recent years. But Amazon.com has grown into an online "behemoth" because it has spent more than £666m on its platform, according to the Forrester report.