what does it do for 10k that my Klein bike I picked up at the salvation army store for $100 can’t do?
Unless you ride a lot of off road rocky trails and long climbs, you won't feel a difference. If you are just cruising around railtrails and roads, it doesn't matter. Off road, it is a beast.
Usually those bikes are the realm of sponsored racers, not everyday mountain bikers.
Okay — I'll put it in terms most on this board can understand — It is like asking what is the difference between a .338 Lapua vs. a Mosin in competition shooting?