Obviously, not all digital multimeters (DMMs) are the same. The wide range of prices tells us that. Then, there are feature differences. For example, as you move up the scale you get high/low/average recording (among other features). An important way DMMs differ is by their energy category.
Suppose you own a computer build and repair shop. Your techs use DMMs to verify power at the 12V and 5V connectors. How much incidental energy is available at the test leads on the typical system that uses a 400W power supply? Even if it’s a gaming system with a large 850W power supply, the DMM manufacturer has a pretty easy job of ensuring the meter can handle the incidental energy. A meter that’s capable of handling this is classified as CAT I.
At the other end of the spectrum, you have a CAT IV DMM. It’s designed to prevent an ionization trail inside the meter, even when encountering the kinds of energy present at a 480V service. Using a CAT III (or lower) DMM here could prove fatal (even if it has a 600V range).
For industrial or commercial work, it’s best to own only CAT IV meters. That way, you’ll never use a CAT III “just this one time” to avoid a “wasted” trip to the shop (a potentially fatal “time saver”).
