Why two dollar stablecoins may not swap one for one

Two tokens targeting one dollar do not guarantee a one-for-one executable exchange. The observed rate reflects their relative market values, pool state, trade size and charges. A difference from parity is not automatically a platform fee.

A relative-value example

Assume hypothetical Token A trades at a reference value of $0.99 and Token B at $1.00. Before execution costs, 1,000 A has a reference value equal to 990 B. A quote of 989 B is one token below that reference, while it is eleven below one-for-one parity.

Calling the full eleven-token difference an execution charge combines the initial relative-value difference with the swap's own shortfall. The reference prices are assumptions in this example, not current stablecoin prices.

Pool balances also affect the quote

Stable-pool pricing depends on balances, amplification and trade amount. A curve intended for correlated assets still has a finite inventory and a size-dependent execution result.

Inspect the reverse direction and quotes at several sizes. A market-value difference can affect even small trades, while deterioration with larger sizes can reveal additional liquidity constraints. Fees may contribute to both observations.

Keep the decision evidence narrow

A pool quote can show the rate currently offered for a particular amount. It does not by itself explain why a stablecoin deviated from its target or prove whether the deviation will recover. Those are separate issuer and market questions.

Report the receiving quantity, the chosen relative-value benchmark and the separate transaction costs. If you also report a gap from nominal one-dollar parity, label it separately. This makes the economic consequence visible without assuming that a token's branding forces its market price or that every unequal stablecoin swap reflects poor routing.