Runtime loaded texture memory too high

Unity Engine
1

I load a 512x512px texture in runtime from disk using www.LoadImageIntoTexture.

var tempTexture:Texture2D;
tempTexture = new Texture2D(4, 4, TextureFormat.DXT1, true); 
...
www.LoadImageIntoTexture(tempTexture);
...

In the memory section of the profiler it gets listed with 8MB!

Using a texture of this format from the editor costs only 341KB.

Why?

2

I test and got the same question in Unity 3.5.6, but if test on Unity 4.1.0f, the texture memory true size