A drive train in a bike works, and wears very similarly to a manual transmission in a motor vehicle.
If you change your gear oil at religiously, install a magnetic drain plug, double-clutch all of your heel/toe downshifts, gently engage the gears and clutch, avoid launches and clutch kicks, you can go past 200k without even replacing said clutch or having to perform any other repairs for that matter.
On the flip-side, you can blow a gear/clutch/etc., out of a brand-new transmission if you're inexperienced, or are running higher power levels, especially when you add aggressive shifting and clutch modulation to the mix.
Bicycles work the same way, very user-dependent...
Personal, I'm around 1000 miles on chains (DA), and double on my cassettes (Ultegra). I shift and put power through my bicycle transmission similarly to how I do so in my sports cars, aggressively, and my component life reflects that.
As others have mentioned, rider weight, rider power, shift habits, riding conditions, and maintenance level will determine how long your components last.