It’s amazing how much bang for the buck a cheap dial caliper can be, but as many of the very experienced guys who measure things for a living have said getting an accurate block or micrometer standard in the 2” to 3” range gives you a better idea of how close your numbers are. Good quality micrometer standards are $20 on fleeBay. I’ve had relatively inexpensive dial calipers since the years when Trump was a Democrat and they have been beat up, jammed up with metal chips, the tips have been used extensively to scribe layout lines on metal, yet the majority of the jaw surface still reads better than it should.
The cheapest digital models, like the $20 Harbor Freight, go through batteries like crazy. There’s a parasitic drain on the batteries that’s just part of the cheap electronics design and the hassle of replacing batteries every 6 months isn’t worth it. Move up to better mid range model, like a $70 Shars digital and that goes away. I can’t say what’s good between $20 and $70, but some probably are. I resisted digitals but they are so handy it’s hard to not grab them first. When checking if all 270 bullets are actually .277” and a 7mm bullet hasn’t snuck in the box, the ability to zero is really nice.
If you’re buying used or new gear online beware of the large amount of counterfeit Mitutoyo stuff. The Chinese con artists really like their designs for some reason. Buy new from a reputable dealer, and avoid used unless the price reflects you might be getting screwed.