I think, as usual, that cost and weight and comfort are all part of an equation that might make certain combinations inpossible. That is, you might have to pay more than $200 for a very light weight bag that weighs less than a kilo (I'm thinking that is a reasonable maximum wt. these days). Campmor is a good place to start if you are concerned with price. I see they have a Marmot Sawtooth 15 degree bag for $180. At 2 lbs, 14 ounces (1.3 kilos)it is a bit heavier than I want to carry, especially in summer. I don't own any Marmot bags (I have 3 down bags and one 3D synthetic fill bag), but their other products I own seem to be of high quality.

http://www.campmor.com/outdoor/gear/Product___46338