They can be worth the money but will only tell you the condition at the location of the sensor. A wind meter gives you the precise condition vs having to guess, but is only a single tool. When using it, don't just take a quick reading. Use it for an extended period of time to observe the predominant conditions, gust strengths, let offs, direction shifts etc. reading the wind should not be a quick measurement but an ongoing activity. A meter gives you great information when used correctly.
The better you understand what is happening over time, the better you can use the information to manage your adjustments and shot timing.