Most people just aren’t equipped to decide how much someone else should earn. Firstly they might be unable to be objective about people they know. Secondly they don’t have the appropriate skills and experience to evaluate someone’s performance.

Due to the first issue, that would make the whole thing a popularity contest. You’d pretty much have to “campaign” to ensure everyone liked you. Who cares about productivity when all that really matters is that everyone likes you.

Instead of voting for someone’s salary, key personnel are evaluated by asking stakeholders to score them on whatever metrics. Stakeholders should include staff and clients and suppliers, et cetera.

Based on their performance you can determine an appropriate bonus.