[klodolph]

It sounded like you were saying that a 0 tolerance resistor would be worth the extra cost, and the reply is pointing out that a 0 tolerance resistor is not actually possible anyway, and as you approach 0, the cost increases beyond whatever your limit is.

[JKCalhoun]

It would seem pretty pointless to try to nail the resistor to within 0% tolerance when the solder bridges, wire that connects them to the circuit will have resistance.

[wildzzz]

You can get really high precision for a resistor at the silicon level but as for a regular resistor, the most you can do is buy the best TCR value you can and laser trim it to the exact spec. You can also buy hermetically sealed that have extremely low TCR and tolerances but they are expensive as hell and are relatively massive. If you can control the temperature of the board really well, you can hit very precise resistance values but again, expensive and not possible for all applications.

Overall, it's much easier to understand where your noise bottlenecks are in your system and cheap out on the parts that won't contribute to any reduction. Like if your ADC has a bit resolution of only 1uV, worrying about noise at the nano volt is just a waste of money.