Yigit Taha OZTURK 
Shortly after midnight UTC on April 8, a Bitcoin user mistakenly paid 0.75 BTC ($70,500) in transaction fees due to a panic-driven use of replace-by-fee (RBF). The transaction was the user’s second attempt to push a prior transaction through by raising the fee and changing the destination address. In the final version, a newly added unspent transaction output (UTXO) ended up being included fully in the fee.
The initial transaction used a “default or conservative” fee setting. The user’s first RBF attempt doubled the fee and altered the output address. But instead of confirming either of these transactions, a final RBF with a dramatically higher fee overrode them, causing the entire amount of the change — 0.75 BTC — to be included as miner reward.
Satoshi Error or Bug in Wallet Script?
According to Anmol Jain, VP of Investigations at AMLBot, the user may have made a simple yet costly mistake in fee calculation. Jain suggested the user likely meant to enter 30.5692 sat, but accidentally typed 305,692 sat — or confused sat/vB with total satoshis.
Another theory is that an automated wallet script contained a miscalculation. Some wallets allow fee settings in sats/vB, and such confusion can arise if the system interprets a small value as too low and prompts the user to increase it. Jain explains:
“User types 305000 thinking it’s 30.5 sat/vB, but the wallet applies 305,000 sat/vB — which is insane.”
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The mistake caused the wallet to treat a full UTXO of nearly 0.75 BTC as a transaction fee, likely due to not properly updating the change address or misreading the transaction structure. Both earlier transactions remained unconfirmed while the highest-fee version went through.
RBF: Flexible Feature or Dangerous Tool?
Replace-by-fee is a controversial but core feature in Bitcoin. It allows users to replace unconfirmed transactions with higher-fee versions. Miners, motivated by profit, are expected to confirm the version that offers a higher reward.
This mechanism has sparked debate. In 2019, Bitcoin Cash advocate Hayden Otto claimed RBF enabled double-spending. Bitcoin Cash removed RBF support and claimed unconfirmed transactions on its network were final and trustworthy.
Despite this, RBF-like behaviors have occurred on Bitcoin Cash as well, showing that this feature is more a result of blockchain dynamics than a standalone switch.
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