Doubt regarding Contour lines of cost function

In week 1 Optional lab of Cost Function, why does a single contour line giving different output? I have attached two screenshots for reference.

It seems the w and b are different so the cost will be different. This is actually a bowl kind of a shape.

I did not get your point. Could you please explain a bit ?

My point is that different points on the line have different weights and biases and hence the cost will be different as you can see from the graph.