Seems like a reasonable price for such a shiny build with the level of components involved, especially with 4 sets of carbon bars and other spares. $7700 is exactly what I would guess it cost to build if you didn't get anything from selling the original parts from the original $2k bike. Probably would not have earned a mention in this thread if it had 27.5/29" wheels, amiright? (Unless someone had bought it and re-posted it the next day for $5000..)
On the other hand, the newer 2020+ Fluid FS 24 (and FS 20) has modern geo and a bunch more travel, comes with a bunch of serious kid-tuned parts. EG the Manitou Machete Junit 24 means it's not compromised by being built around a 26" fork (but also that you can't convert it to 26" later.) I got a 2021 FS 24 1 for a lot less than this 2013-2019 Fluid FS 4.1.