What determines a blockchain transaction fee

A network fee pays validators or miners to process an operation. In many blockchains it depends on demand for block space and the complexity of the action.

A simple native-coin transfer and a smart-contract interaction can cost very different amounts. An exchange or wallet may also add its own fixed withdrawal fee.

Compare the final amount, network and confirmation time. A cheaper network is useful only when the recipient actually supports it.

Do not save fees by sending an asset through a similar but unsupported network. A network-selection error is usually much more expensive than a normal fee.