A Klein Quantum "purple haze" updatet with Carbon Weels, the Shimano 105 R7000 Groupset and many new lightweight parts.
Costs:

Second Hand Bike complete 700.- Euros
Second Hand Wheelset 250.- Euros
All new Parts 1500.- Euros
Minus sold parts:
Shimano Groupset 115. Euros
Wheelset (Chris King) 650. Euros
Total= 1685.- Euros


I'm not a pro mechanic so some things are not perfectly executed, but you get the idea.