Okay, I can explain my arsenal pretty well.
I have my main bike, my Pista.
Now, as I upgraded that bike, I collected parts and eventually had enough to build a second bike. Did that, and now the trickle-down process keeps going. The Pista is done, officially. So, now as the Pake upgrades, the Sekine or some new bike will get its parts.
All very economical.