Is Subsurface Scattering expensive?

Just decided to give another try to the default udk subsurface scattering feature and wanted to ask, is this expensive to place on every character in game?(that has skin obviously )
Up until now I have been using only transmission mask and transmission color to fake skin.(took the idea from the beneath udk demo fish guy).Also tried some random dx9 udk skin shader ive found.

I didn’t see a significant cost, but it does slow down when using DX11. In that mode, turning the sss on or off was more or less the same in speed.

What I noticed is that in DX11 you lose the specularity in the materials and a way to fix that was activating in the material the sss option, even if you didn’t use the slots. Apparently at no significant cost in performance.

That, about the specular in dx11, I didn’t knew .Thank you for the fix.Will see if custom lightning specular also helps in dx11.