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My experience through a 25x loupe is that, on a high level...
4k after circles looks like a heavily fogged mirror.
8k after circles looks like a lightly fogged mirror
12k looks like barely scratched chrome (think like very very lightly weathered chrome strips on a car). To the naked eye 12k looks like a mirror finish.
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Good optics are expensive. However it's an investment like a good hone or a good strop or even a good razor. Once you buy it, it will last longer than you. A quality 30x magnifier is all you need.