Puffy pants?

[Lowg08]

You could hunt down a used pair of Sitka Kelvin pants. They're really warm.

x2 on these

 

[ozyclint]

x2 Nunatak like mtwarden said

 

[Mike Islander]

For a good combo of cheap, light, and warm, check out the True Timber Pulse puffy pants. I like the Strata Camo, and they are cheap enough to not worry too much about them on a hunt. I think I paid $60ish for mine, hunting partner has a pair too. They are 3/4+ zip. My larges weigh around 11 oz.

They're that price because they are 90% feathers and only 10% down. Not what I would call a true puffy, but I am a down or primaloft-style insulation fan.