* IPO prices at $10.50/share, 30 pct less than estimate

* IPO raises $141.75 million (Adds other analyst comment, background on company)

By Phil Wahba

NEW YORK, April 14 (Reuters) - Bridgepoint Education Inc, (BPI.N: Quote, Profile, Research) an operator of online and campus universities, became the third U.S. company to go public this year, but priced its deal 30 percent below the midpoint of its estimate range of $14 to $16, a source with knowledge of the deal said on Tuesday.

San Diego-based Bridgepoint sold 13.5 million shares for $10.50 each, raising $141.75 million, the source said, far less than the company's original estimate that the IPO could raise as much as $216 million.

The deal's structure, in which most of the shares were sold by an existing shareholder with very little money going to the company, and a recent drop in the stocks of Bridgepoint's rivals caused the deal to be priced less than expected, an analyst said.

"There are two reasons that I see derailed an offer whose numbers at first glance looked outstanding. First, the amount of insider selling, and second the stocks of the comparables have fallen," said Scott Sweet, senior managing director with research firm IPO Boutique.

About 81 percent of the shares being sold are held by private equity firm Warburg Pincus.

Rivals Grand Canyon Education Inc (LOPE.O: Quote, Profile, Research) and Apollo Group (APOL.O: Quote, Profile, Research) have seen their shares drop about 22 percent and 30 percent, respectively, since their January highs.