Measuring the value is very difficult. However there are proxies (of varying quality) which are measured, and they are showing that AI code is clearly better than copy-pasted code (which used to be the #1 source of lines of code) and at least as "good" (again, I can't get into the metrics) as human code.

Hopefully one of the major companies will release a comprehensive report to the public, but they seem to guard these metrics.