Not sure if this the cheapest but a really good deal judging from previous post.
Also, Macpac Halo Down Jacket - Men's for $79.20+$10 delivery
The legendary Halo down jacket — now with a hood. The hooded Halo is an excellent all-rounder, perfect for wearing while you're out exploring the city, travelling the world or camping in the wilderness. Filled with 600 loft Responsible Down Standard (RDS) duck down and featuring elasticated cuffs and an adjustable hood and hem, this jacket works to keep you warm by trapping heat against your body. A durable nylon shell protects against general wear and tear, while the internal draft tube and soft chin guard aids insulation and overall comfort. A separate stuff sack is included for convenient storage when not in use.