The cost to manufacture Amazon.com Inc.'s (AMZN) Kindle 2 electronic book reader is "significantly higher" than a recent market researcher suggests, the ecommerce giant's chief financial officer said Thursday.

Tom Szkutak was commenting on a report by research group iSuppli Corp. that suggested materials and manufacturing expenses for the Kindle cost about $185.49, about 51% of the unit's retail price of $359.

Szkutak made his comments in a call with reporters after the company reported strong first quarter results but provided slightly disappointing second quarter guidance.

Szkutak declined to provide additional details about the cost of the device and the company once gain refused to reveal how many Kindle units it has sold.

-By Scott Morrison, Dow Jones Newswires; 415-765-6118; scott.morrison@dowjones.com