What does server-authoritative mean in FiveM?

The property is binary at every handler. Either the server worked out the fact itself — looked up the price from its own config, checked the player's job from its own records, computed the payout from its own timer — or it took the client's word for it. There is no partially authoritative event; a script can be authoritative in ninety-nine handlers and lose the economy through the hundredth.

It matters because the client is not yours. A player's game runs on their hardware, and tools that trigger arbitrary server events with arbitrary arguments are common. A handler that reads `amount` from a client event and adds it to a balance is not a bug waiting to be found; it is an ATM. The same applies to positions ("I am at the drop-off"), states ("I am on duty"), and identities ("I am the owner of this vehicle") — anything the client asserts must be re-derived on the server.

You can spot the opposite without reading escrowed code. Ask the seller how each money-moving or permission-changing event validates its source, permission, rate, and argument types; a seller who cannot describe that has not done it. On an open resource, search the server files for handlers that use a client-sent number directly. On staging, trigger the events yourself with wrong arguments and see whether the server refuses. That last test is the only one that does not depend on anyone's word.