If you compare the rate on a non-custodial exchange to the rate on a large centralised exchange, the centralised exchange will almost always be better. The spread — the difference between the mid-market rate and the rate you receive — is larger on non-custodial platforms. This is not an accident and it is not a failure. It is the cost of the architecture.
Understanding what you are actually paying for makes it possible to decide whether you should pay it.
What the spread covers
On a large centralised exchange, your trade is executed against an order book. The exchange matches buyers and sellers directly. The spread can be very tight because the exchange is not itself taking on price risk — it is connecting parties who are.
Non-custodial exchange works differently. Liquidity is sourced from aggregated pools. The exchange provider — in Terce's case, via the ChangeNOW API — takes on short-term price exposure during the settlement window. The spread compensates for that exposure. It also covers the structural cost of operating without custody: no account revenue, no interest on held funds, no withdrawal fees.
The spread is not overhead. It is the product. You are paying for a transaction that leaves no record, requires no identity, and involves no custodian.
Major CEX spread (BTC/ETH): 0.05–0.1%
Difference: 0.25–1.4% — the cost of non-custodial settlement
For most people doing most exchanges, this difference is small in absolute terms. On a $1,000 exchange, the additional cost is $2.50 to $14. Whether that is worth paying is a question only you can answer — it depends on what value you place on the absence of a record.