A teardown of HTC Thunderbolt by research firm HIS iSuppli reveals the 4G LTE wireless component within the phone added a $39.75 to the total bill of the material of the smartphones.

Most of this expense come from a first-generation LTE baseband chip, Qualcomm MDM9600.

With a BoM of $262, Thunderbolt has the highest manufacturing cost of any smartphone HIS has ever torn down. It almost rivals the cost of full size tablets and this could have a significant impact on the BoM of any 4G-enabled iPhone 5 and profit margins of Apple.

Recently an analyst said that Verizon’s HTC Thunderbolt was more popular than the iPhone at Verizon stores.

By adding 4G to the iPhone, the price of iPhone 4 will increase by around 23 percent, without including any cost related to design changes or modifications to other features.

Qualcomm is certainly going to be the provider for any LTE part and it will be interesting to see whether Apple actually gets an integrated CDMA/HSDPA/LTE chipset, the first of its kind.

However, it’s surprising to see that Verizon may be planning to give away HTC Thunderbolt for free in an upcoming promotion.