You’re not looking at it from a business standpoint. For the majority it has nothing to do with trashing the kart. You can go to any major event and there with be a company out there with arrive and drive opportunities. I spoke with one of these companies at this years USPKS race at the GoPro Motorplex. For a 100cc or 125cc kart the arrive and drive cost was $2000 plus you had to buy two sets of tires, fuel, and usables. You had to pay your own fees ofcourse. You also had to have your own mechanic or you had to hire one from the renter. From a business standpoint this guy isn’t selling one race chassis since he has a big rig and does this as a business. His fees are high since he runs a business renting ready to drive race winning karts.
Now look at a local shop or outfit, maybe even chassis maker who has some hot shoes who want to race. He jumps on a $7000 setup and pays $3000 or so to run the weekend. They just recouped a big portion of the cost. They then part out the one race chassis and motor and all the other parts to break even or make a small profit. Most of these one race chassis come from people who aren’t trying to screw you but recoup some of their cost.