Do manufacturers try make their components as close to ideal ones as possible?
Yes - but to a budget.

For example, in the case of resistors, there are various tolerances available which tell you how much the actual ohm value may differ from the stated value. 5% tolerance used to be standard, these days 1% is not significantly more expensive. If you want a 0.001% tolerance resistor you'll have to pay more. Similar things apply to the temperature coefficient of resistors.