Witness the wasted rear tire on my "nice weather" carbon Ibis. It's a Michelin Lithion, 23c to be exact. I'm guessing about 4000 miles to toast this tire. Not too bad really. The front tire is still useable, though I usually replace both tires at once.
I love wearing bike parts out. Seeing the cords poke through is proof of the miles being ridden, fitness being gained, fun to be had, adventures experienced - and money saved. What? Another set of tires to buy is money saved?
Considering almost all of my road miles are commuting miles, springing for new tires - compared against gas, parking and other car costs - bike tires seem almost free. It's pretty easy to justify nice bike goodies when it involves getting your ass to work.
Besides the money savings, bike commuting kills sitting in traffic or in a bus - hands down. No comparison.
I can't wait to start wearing out the next set ....