Nick is right about paying for quality parts once. Those who have purchased low cost parts only to repair and replace them, ultimately buying the quality part they should have bought in the first place, learn that lesson. But its not that simple always.
Aussie is also right that your car (or engine) is not just the sum of its parts. Craftsmanship, attention to detail, tuning, maintenance, driver, are all major factors in reliability. You can buy the best of everything and still blow it up because you forgot to torque that rod bolt, or your tuner forgot to sync ignition, or you ran a low on fuel and sucked air during that late night hwy pull - there's a million reasons. Some guys get lucky and get it right the first time. Some of us spend our lives and tens of thousands of dollars chasing the dream.