Four 7970s in CF setup:
$430 * 4 = $1720
And toss in another $1000-$2000 for extreme watercooling to OC the heck out of the monster setup. And that's still nowhere close to the 6990's inflated price.
Anyone that tries to explain how a 6990 priced at
the so-called suggested retail price of $7459.19
$5967.35 despite being second-hand can do better than four highly OC'ed 7970s is either delusional and thinks that it's still the early 2000's, or is a very persuasive person.
EDIT: Web of Trust gave that website a low rating in Trustworthiness category. I wonder why.