Juanhanded: Just because a part is made by the same manufacturer means the parts are the same quality. In you pulley example the bearing is the most critical part. Most bearing manufactuers are capabable of producing bearing of varying quality (life expectancy) by changing the material make up of the bearing or producing a bearing to closer tolerance levels - like a Good, Better, Best. How could you determine that by looking at them. I worked for a lift truck company that built their own motor controller that used power transistors that were relatively expensive. They saught a new supplier that offered one at a lower price (but at a wider tolerance operating range). The results were catastrophic. Remember you get what you pay for. Also it is not uncommon to get different selling prices for the the same part at differnt dealers (auto & forklift). In the forlift business it is common that dealers will sell parts above the manufacturer's suggest list price.