The deal is available for all major carriers in the US that sell the devices – Verizon Wireless, AT&T and Sprint, with a two-year-contract.
The 16GB iPhone 5 is now priced at $149.99, the 32GB iPhone 4S is sold for $249.99, while the 64 GB version is on sale for $349.99.
Also, the iPhone 4S now starts at $49.99 instead of $99.99.
According to a Best Buy spokeswoman who spoke to CNET, the offer is available through January 5 and is limited to two phones per person.
Last week Best Buy offered a free $25 gift card with the purchase of any iPhone 5 with Verizon, AT&T or Sprint on a 2-year plan.
Source: Best Buy