Does 0% maker and 0% taker on KCEX spot mean your trade is free? How to measure the cost that is still there

No. KCEX lists 0% maker and 0% taker for spot, so the commission line on a normal spot fill reads zero, but the price you actually get can still sit well away from the price you saw when you decided to trade. That gap has a name, implementation shortfall, and it is worth measuring before you assume a zero-fee pair is costing you nothing.

The image shows a logged-out KCEX spot trading page with the live order book, where the space between the best bid and the best ask is the first cost a market order pays.

1. Start with the spread

Take a made-up book: best bid 99.90, best ask 100.10. The midpoint is 100.00 and the quoted spread is 0.20, or 0.20% of the midpoint.

• Buy at market right now and you pay 100.10, which is 0.10 above the midpoint.
• Sell at market right now and you get 99.90, which is 0.10 below it.
• Do both at unchanged quotes and the round trip costs 0.20 per unit, with a commission of zero.

These are example numbers, not a live KCEX quote. The point is that "no fee" removes one term from the bill, not the whole bill.

2. Pick the benchmark before you trade

Implementation shortfall compares the price at the moment you decided against the average price you actually filled. For a buy it is (average fill minus decision price) times filled quantity, plus any commission and the cost of whatever never filled. For a sell the sign flips.

Write the decision price down first. If you pick the benchmark afterwards, you will pick a flattering one. A simple log has these fields: timestamp with time zone, pair, side, intended size, decision midpoint, order type, limit price, filled size, average fill, commission and a later reference midpoint for any unfilled part.

3. Worked example with a partial fill

Example only, not a real KCEX fill. You decide to buy 100 units with the midpoint at 100.00.

• 80 units fill at an average of 100.20, so slippage is 0.20 x 80 = 16.
• Commission is 0 under the 0% spot schedule.
• 20 units never fill. If you value them against a later midpoint of 100.50, the missed move costs 0.50 x 20 = 10.
• Total shortfall under that method: 16 + 10 = 26.

Change how you value the unfilled 20 units and the answer changes, so fix the method once and use it for every trade.

4. Market vs limit is a trade-off, not a right answer

A market order buys certainty of execution. In a fast drop, paying the spread to get out can be cheaper than waiting on a passive sell that never fills. The catch is size: if the best ask only holds a few units, the rest of your order walks up the book and your average price gets worse. A 500 order and a 50,000 order in the same token can see very different slippage even though both pay zero commission.

A limit order can earn a better price, but it carries fill risk. The market can run away and leave you with nothing, or rip through your level and fill you right before it keeps going. Judging limit orders only on the fills you got, and ignoring the ones you missed, makes them look better than they are.

5. Read the book, not just the fee page

• Note the spread, then add up bid and ask depth within a few bands of the midpoint, for example 10, 25 and 50 basis points. A basis point is one hundredth of a percent.
• Compare your order size to that depth. Size relative to visible depth says more than the dollar amount: 5,000 is nothing on BTC/USDT and a lot on a freshly listed token.
• Check the same pair at different hours and on weekends. Depth is not constant around the clock.
• Expect spreads to widen and depth to thin around big data releases and token news. The zero-fee saving stays, but impact can swamp it.

6. Review it weekly

Group fills by pair, side, size bucket and calm vs busy conditions. Look at the median shortfall and the worst tenth of trades, keep maker and taker fills apart, and note partial fills. Also keep in mind that fee schedules and pair-specific terms can change, so a backtest that assumes 0% forever may not match what you pay later.

Takeaway: zero commission is real on KCEX spot, but your true cost is fee plus spread plus slippage plus missed fills, and only your own log will tell you that number.

$BTC.USDT $ETH.USDT $SOL.USDT $XRP.USDT $DOGE.USDT