Definitely with Edge on this one. You don't really build a rifle in order to save money (so to speak). You're usually building it to get exactly what you want right out of the gate. When you buy the off-the-shelf rifles, you're going to slowly (or quickly) start swapping out parts to get what you want anyway. Every rifle that I build usually has a specific purpose, or a specific look that I'm going for. And, like Edge said, I usually don't need to change any parts once I get them together.
Oh, and the OBR/SR25/AR-10 SASS style rifles can get up into the teens (in weight) pretty easily once they're dressed out with glass and a bipod (no...not the Elite Iron one either)...especially with full 20 round mags.