At the wallet level
Nothing prevents wallets from implementing reasonable safety measures to protect users from undesirable behavior.
For example, Bitcoin Core has a feature that essentially refuses to create transactions with very high fees. There are no specific rules preventing fees being higher than the amount transferred, but there may be. Other wallet software may have similar or different precautions.
At the policy level
Policy rules exist to protect the network, not individual node operators. Rules preventing fees that are too high don’t belong here as they don’t harm the network.
Besides, it is Stiff The amount paid/transferred is by design It is not visible to the transaction (most transactions have changes sent back to the sender, but are indistinguishable from the “payment” output that is sent to outsiders).
Dust relay rules are intended to discourage the creation of more costly transaction outputs. guard These outputs, more than they are worth, will likely remain unused in the UTXO set forever, slowly accumulating, ultimately increasing the cost of running the node.
At the consensus rule level
The same considerations apply here as for policy rules. However, it requires the consent of the entire ecosystem and is much more difficult to change.
Until now, this meant that there were no rules surrounding fees at all (except the requirement that they be non-negative). This is partly due to the fact that “rational” economic behavior can change over time, i.e. over a much shorter period than the period over which consensus rules can apply.