^^
They stopped using "real tweed" before 2010. They have done an incredible research over the years to make the tweed lighter.
First, they used different materials to make tweed (I remember that they did a silk and polyester tweed) and Karl asked Linton (their supplier) to develop new ways of doing tweed and over the years, the Chanel tweed became quite shimmery and all.
In the 90's, Mr Lesage wanted to develop his affair and established a workshop. In the late 90's, he presented his "tweed" to Chanel and ever since then, they have used Lesage tweed in their collections. I think it was also instrumental in them buying Lesage, as they have the exclusivity to this tweed.
Since 2008, Lesage does tweed for all Chanel collections. That's why it's so expensive and why there are so little differences between Couture, Prefall and main RTW collections.
In addition to that, now they are doing tweed embroideries on an Organza base. But i think they are using those techniques only in Haute Couture and for special RTW pieces.
In the first video, you can see how light is the tweed developped by Linton.
In this video, the way Lesage weaves their tweed.
At 0:53, you see how their embroideries to make it look like tweed and at 1:43, their tweed on organza
At 1:59, another showcase of their technique of "tweed".