I built a ROG Zephyrus equivalent: The ROG is $2,100 and the Framework is $2700.
So its more expensive but not $1500 vs $4000 expensive.
This was comparing the lowest end model ROG because that's the only one with a 5070. It was also 100% like-for-like, such as paying for windows, something I personally wouldn't do with a framework.
Judging by my experience with the Framework 13, you gain basically nothing going pre-built. The DIY work required is laughable. It's so, so easy and simple. If you don't account for nervousness, you could do it in 5 min, no problem. Comes with a very nice little screw driver, which is all you need.
So its more expensive but not $1500 vs $4000 expensive.
This was comparing the lowest end model ROG because that's the only one with a 5070. It was also 100% like-for-like, such as paying for windows, something I personally wouldn't do with a framework.