A bitcoin transaction moving a large sum can cost less than one moving pocket change. Fees are priced by the space a transaction occupies in a block, not by the value it carries.
Block space is the scarce good
Each block has a hard limit on how much transaction data it can hold, and that limit does not change when demand rises. Miners fill the space with whatever pays best per unit.
Because the constraint is space, the natural unit of price is the fee divided by the transaction's size, usually expressed per virtual byte. Wallets quote that rate rather than a flat charge.
The amount being moved never enters the calculation. A payment worth a house and a payment worth a coffee compete on identical terms if they occupy the same number of bytes.
Inputs are what make a transaction large
A bitcoin balance is not a single number but a collection of previously received chunks. Spending requires naming each chunk you consume, and every one adds data and a signature.
A wallet funded by many small deposits therefore builds fat transactions. Someone who received a single large deposit can spend the same total with one input and a fraction of the size.
Outputs add size too, though far less than inputs. Sending to several recipients at once is usually cheaper in total than sending several separate transactions.
Consolidation is a timing decision
Combining many small chunks into one large chunk is itself a transaction, and an expensive one, because it names every input being swept. The cost is paid once rather than on every future spend.
The practical approach is to consolidate when the network is quiet, since the same operation costs whatever the going rate per byte happens to be at that moment.
Very small received amounts can become uneconomic entirely. If a chunk costs more in fees to spend than it is worth, it sits in the wallet as dust that will not move.
How wallets estimate the going rate
Wallets watch the queue of unconfirmed transactions and estimate what rate is currently clearing. The estimate is a forecast about the next several blocks, not a quoted price.
Because blocks arrive at irregular intervals, an estimate that looked generous can become inadequate within an hour. A quiet stretch followed by a burst of demand strands transactions that were priced for calm.
This is why wallets offer a slow option. Paying a low rate is a bet that the queue will drain before the payment matters.
What the pricing model rewards
The design pushes users toward fewer, larger, better-structured transactions rather than many small ones. Address formats that encode signatures more compactly are cheaper for the same economic action.
It also pushes small everyday payments off the base chain, since a coffee-sized transfer pays the same rate per byte as anything else competing for the block.
The rule is consistent from the miner's side: block space is inventory, and inventory is sold by the unit, whatever the buyer happens to be shipping in it.