Just had a look at the test setup and back then (2010) that gear was high end stuff, which tells me that in order to enjoy SLi the way it's intended, the outlay is rather high.
And to gain fps that your human eye won't even notice, personally I find that there is little to no value for money with these setups.
Again, if you are happy with SLi then fine, just not for me and I find it upsetting that marketing makes you feel like you "need" this as a gamer to play certain games better (as long as it has a SLi profile), and then have new hardware pop up that "blows previous cards away".
I know if you were to wait for a definitive card you'd wait forever, thus I usually wait till the newest one comes out and pushes the price down on the previous "top dog".