On the pockets degree
Nothing prevents wallets from implementing cheap security measures to guard their customers from undesirable habits.
Bitcoin Core for instance has a characteristic to (by default) reject the creation of transactions with a really excessive charge worth. There isn’t a particular rule to forestall charges increased than the quantity transferred, however there definitely could possibly be. Different pockets software program might have comparable and/or completely different preventative measures.
On the coverage degree
Coverage guidelines exist to guard the community, not the person node operator. A rule to forestall too excessive charges would not belong right here, because it would not damage the community.
Moreover, it’s laborious to think about what such a rule would appear to be, as a result of the quantity paid/transferred is by design not seen within the transaction (most transactions have change that’s despatched again to the sender, however which is indistinguishable from the “fee” output to outsiders).
The mud relay rule is meant to disincentivize the creation of transaction outputs which might be dearer to spend than their worth. Such outputs are prone to stay unspent within the UTXO set eternally, slowly accumulating and finally growing node operation prices.
On the consensus rule degree
The identical concerns apply right here as for coverage guidelines, besides they should be agreed upon by your complete ecosystem, and are such a lot more durable to alter.
To date, this has meant no guidelines in any respect that relate to charges (aside from requiring them to be non-negative). That is partially as a consequence of the truth that what’s “cheap” economical habits might change over time, at timescales a lot shorter than these over which consensus guidelines might be tailored.
