They were a pair of Leadtek Winfast 256mb PX6800s & back when I bought them were £200 each & tbh, I wasn't overly impressed right from the start.
SLI was in its infancy back then & the board I bought was one of the first to support it: ASUS A8N SLi Deluxe & if you know the board or research it via google it was probably the worst ASUS board ever although personally, after 6 BIOS updates & 6 months of being treated like a guinea pig & swapping the NB fan for a heatsink I managed to get it running stable.
I only did SLI coz I wanted to know what it was all about & a tasty tax return funded it.
Now they are doing triple & quad SLI which is going to the extremes & I'll never do it again coz like you say, the cost of doing it outweighs the gains, I'd rather buy an xbox 360 than spend a further £200 on a 2nd gfx card that will be out of date in 3 or 4 months time.
Primitive effects to me are polygons. I dont understand a lot of the physics but what I prefer about COD4 to Crysis is the fact that I can run it on max detail & feel warm & fuzzy knowing my latest piece of hardware is doing what I expected it to & yet crysis wants me to spend even more money which I wont do & by the time I do I expect crysis 3 will be on the shelves & the card I replace this with wont run that on full detail either.