How many times have you played a guitar that just doesn’t buzz however you play it? It has a percussive slap back if you dig in but absolutely no fizzle after? This is perfect level frets and a perfect relief contour. The guitars that have it are gold and you can’t really guarantee that by hand unless you are prepared to do multiple passes with strings on in between and have the skill to evaluate the results . Nobody is going to do this for anyone but themselves. On my guitars I can do this over several weeks playing it extensively in between tweaks. Some necks simply aren’t capable of doing it because the flex is not ideal or over time they always give in to pressure from compression and flex producing a gradual change in geometry.
My Hydra was perfect without touching it but it has an engineered neck. By that I mean multiple layers of different wood selected for stability, a non compressing truss rod , carbon reinforcement and an ebony fingerboard. It also has a six screw attachment and the thicker heel.
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This doesn’t move and is perfectly predictable.
My Vigier was also perfect from the box.
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The 10/90 neck is utterly ridged and totally predictable. My Aristides guitars too by the fact that they are not wood.
The first time I ever encountered this “perfect” neck was a Jackson custom made Soloist in the mid 80s I absolutely had to have it.
How often is this out there in the wild you may ask? Not many would be my guess. Does paying for a high end guitar guarantee it? No but it massively increases the chance. For me this is one of those things found in the last couple of percent that makes the difference in an exceptional instrument along with no dead spots and a musical resonance . Good luck finding one ( I have them all )

Including my Suhr Modern which is the least modern guitar I own.