I use cheap $25-$30 digital calipers. The trick isn't so much in how accurate they are, but how well you know how to use them. Most all cheap ones are easily accurate to within .001", which is plenty fine enough for cue work. My butts & shafts are never sanded together to blend before finish. They mate up just fine right off the lathe, cut to the same dimensions as measured by my el-cheapo calipers. By the time I apply the finish and sand/polish with the sanding arbors, if there was ever any slop then it's gone. Sure you can say that makes the finish thicker on one side or uneven but we're talking dimensions too small for human eyes to see in the first place so it doesn't matter. The only bennefit I can see to getting expensive calipers would be ease of use, longevity, more options, etc. With cues I simply don't think accuracy is an issue. I know one known veteran builder who buys cheap calipers every couple of months. When the battery dies he buys new calipers instead of new batteries. I have NEVER heard anybody mention the accuracy of his work in a negative way.