Given that the frame set only price is $4600 I’d say it’s reasonable but I would ask the seller a few questions. It’s kind of an odd collection of parts. It looks like it’s an upgraded seat, headrest (pictures of original in the ad) and boom but no shifters or cassette plus MTB bars. I can’t think of how you’d end up with that assortment. Buy a frame set but before you’ve even built it upgrade the seat, change the boom, etc?
Also, the ad says the front caliper is damaged. I’d ask what the damage is and what caused it.
If you’re handy and able to do your own work it would be a reasonable buy. You’re likely going to have to spend some money to get it on the road but not an outrageous amount.