It's not how much it's going to cost...now. "Now" will set you back $300-400 US dollars but a week after you build it you're going to want to tinker with it...to buy a fan controller that ties CPU temp to automatic shut-down sequences should it get too hot. You're going to read something in a review about this cool reservoir and you'll go buy it. You'll see some new compression fittings that scream "buy me"...In a month you'll decide that the wiring in your newly-great looking PC should be sleeved and you'll spend another $100 and countless hours re-sleeving so your PC can be amazing looking (you get so jealous of those guys who can make a PC look sexy at MDPC it kills you).
Welcome to the Twilight Zone...erm...the Cooling Zone...where rationale thought is pushed aside in favor of a pure unadulterated compassion to get the next "Cooling High"...welcome to the club.