Resistor is more than resistance. There is also other characteristics like power capacity, accuracy, tolerance, frequency responses, temperature coefficient etc

Resistor is more than resistance. There is also other characteristics like power capacity, accuracy, tolerance, frequency responses, temperature coefficient etc. The cheaper resistors are typically very loose for most of these characteristics. A tight characteristics means a high level of quality control at manufacturing, and this is usually lacking for the fakes. For Op-Amps, the interesting spec is their frequency response as the op amps are not typically used in DC situations.