As one who definitely believes in the KISS method, I don't see the point in spending very much for parts that will not see that much stress or hard use. I have more than one AR, and each of them have started out as cheap Bushmasters. One has been upgraded moderately, and another has had most of its parts replaced with higher quality parts out of necessity.
Having said that, if I had to trust my equipment with my life (military, law enforcement, security, etc...), I guarantee I would spend whatever I had to in order to feel comfortable with the quality and reliability of all my tools. I would only use items that are widely used by my peers and that have had the least amount of reported issues.
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