Complex sentence: Because it is no longer for sale, original copies are considered a rarity, however, in 2006 Best Buy offered a DVD version for free for a limited time with purchases of "The Essential Alice in Chains".
Split into simpler sentences: Because it is no longer for sale, original copies are considered a rarity. However, in 2006, Best Buy offered a DVD version for free for a limited time with purchases of "The Essential Alice in Chains".