Each input of the transaction requires a signature, which makes the transaction larger and therefore increases the required fee. Here is a random example from a

Each input of the transaction requires a signature, which makes the transaction larger and therefore increases the required fee. Here is a random example from a recent block of such a transaction with many inputs, it pays about $52 in fees: https://blockchain.info/tx/ef29f862f3ceee10ed3e1f04585e18cc28a7915e2e62419e714549a4185fbdc5 https://blockchain.info/tx/ef29f862f3ceee10ed3e1f04585e18cc2... So it is more accurate to think of the cost as a fee per byte instead of a fee per transaction. And there's a minimum amount of bytes that's needed to consume any hitherto unspent transaction output. Interestingly, if bitcoins were to support Schnorr signatures, then the signatures could be combined and then your idea would work. Though this would not be able to salvage the existing unspent transaction outputs that are already secured with ECDSA signatures.