A 70,000 mile Prius is just hitting its stride. My 2006 just passed 250,000 miles. Aside from tires and wiper blades, and normal scheduled maintenance, I've had to do exactly three repairs:
1. Rebuilt the brakes (pads and rotors) at about 150,000 miles
2. At 248,000 miles, the hybrid battery finally died. $3,500
3. At about 100,000 miles, the ABS controller failed. This was complicated to diagnose, and expensive to repair. Don't remember the cost, but I think it was a bit north of $1,000.
Everything else, even the 12V battery, is still original. This ignores the repair of significant collision damage, since that was my fault, not the car's. Even that tells you something about the Prius, though. I hit a big SUV. My front end was crumpled, the SUV was totaled.