Macrumors is reporting that Apple has significantly reduced the build cost of the CDMA based iPhone 4 with some design tweaks. The CDMA variant of the iPhone 4 carries a BOM of $171.35, down from $187.51 for the original iPhone 4, based on a preliminary pricing estimate issued in June. More on that, after the break.

When manufacturing costs are added, the total production cost for the CDMA iPhone 4 totals up to $178.45. The reason behind this are significant changes in Apple's design and component selection for CDMA iPhone 4.
Research firm IHS iSuppli did a complete teardown of the CDMA iPhone 4 and had this to report:
Despite having nearly the same functionality and a similar bill of materials (BOM) as the previous model, the new code division multiple access (CDMA) version of the iPhone 4 carried by Verizon Wireless includes significant changes in its design and component selection
The latest version of the iPhone 4 carries a BOM of $171.35, down from $187.51 for the previous model, based on a preliminary pricing estimate issued in June. When manufacturing expenses are added, the total production cost for the CDMA iPhone 4 amounts to $178.45.
The attached table down below shows the preliminary IHS iSuppli estimate of the bill of materials (BOM) and manufacturing costs of the CDMA iPhone 4.

Please note: This cost assessment of the CDMA iPhone is essentially preliminary and takes in to account only the hardware costs and does not include other expenses such as software, licensing, and royalties or other soft expenditures.