Yes, totally agree on the risk front but there are plenty of second hand bikes available that have barely every been ridden. If you’re lucky enough to find one of them or buy a previous season model direct from the manufacturers shop.
Well Giant are great and manufacturer their own frames to very high standards but Ribble frames like Planet X are sourced from some pretty decent CF factories in the far east like many of the major US and EU brands who often charge a lot more. However there is still the issue if buying secondhand you don't know the history of the frame and forks and most people don't bother to scan CF frames and forks they purchase so its much more of a gamble even with Giant.
Decent although with a bit of effort and luck you could find a great bike second hand for that money. I picked up a Giant TCR with Ultegra for not much more than that.
I have this bike but with the 105 Group set. Absolutely love it (y)
plus delivery which is a lot