Framerate is not linear, so you shouldn't use it to determine performance impact. Going from 1000 to 700 fps is equivalent to adding ~0.4ms of frame time, while going from 700 to 500fps is equivalent to adding ~0.6ms of frame time.
AMD has GPU ShaderAnalayzer which can convert your HLSL to actual hardware-specific microcode (not D3D shader assembly, which is just an intermediate format) and can give you cycle counts for the shader. But overall performance at runtime is still going to vary based on a lot of things, such as how many pixels you shade or what else is currently executing on the GPU.
Exactly what I was looking for,thanks.I was planning to use a parallax normal mapping on every object in my game,so I was curious at how heavy the technique actually is.