Why is employee reputation needed?
If you make a lot of mistakes, then the system blocks you, but not forever, but before being checked by a moderator. The moderator assesses whether you made mistakes on purpose or by accident, how often you make mistakes and makes a decision: to block your account forever, send you to training again or remove the block. When evaluating, the moderator sees the user's reputation and is more loyal to users with a high reputation.
How to get reputation?
Now for entering 1000 captchas 1 unit of reputation is credited
Does reputation affect the cost of a captcha?
No, only the system load affects the cost. When a lot of captchas are sent to the webmaster's system, and there are few employees, the cost rises for both employees and webmasters. However, sometimes you can earn more on recaptcha / moderation / checks than on regular captchas.