Hello. The earnings is depending on the voters Steem Power and Voting Power. The more they have the more their vote worth.
You can check your (or someone else's) voting power and how much the voting is worth on external sites.
Useful Links:
https://steemit.com/steemit/@xplosive/some-great-steem-tools-check-your-voting-power-and-your-potential-pending-payouts
https://steemit.com/steemnow/@penguinpablo/steemnow-com-new-feature-how-much-is-your-upvote-worth
https://steemit.com/steem/@tuck-fheman/how-is-voting-power-determined-in-steem
https://steemit.com/steem/@xerxes612/you-voting-weight-is-too-small
I hope that these helps!
Enjoy Steemit! Have a nice day!