yeah, as best I can tell you absolutely can pay someone more if they are better at their job under equal pay laws.

In California for example, the equal pay act requires 'equal pay for employees who perform “substantially similar work,” when viewed as a composite of skill, effort, and responsibility.'

https://www.dir.ca.gov/dlse/California_Equal_Pay_Act.htm

Someone who contributes more inherently must have greater skills and/or put in greater effort, and likely greater responsibility, given they are accomplishing more tasks.

You can pay differently based on a seniority system, a merit system, a system that measures earnings by quantity or quality of production, or another bonafide factor such as education, training or experience.

Here's a copy of that law, it's pretty short.

https://leginfo.legislature.ca.gov/faces/codes_displaySectio....