When trading low-priced coins, you may occasionally see a warning that the estimated fee greatly exceeds your current fee rate. In the example below the displayed fee is 10% of the order amount! Why is this happening?
Don’t worry, you won't have to pay that much. What you see is the worst-case scenario. Although it is highly unlikely to happen in real life, HitBTC engine has to calculate the fee and display it to you.
In every trade on the exchange, one of the participants (or both) is paying a reasonable fee (you may check your fees here). But if the trade amount is very low and the coin is very cheap, the fee can become incalculable, less than a satoshi. In such a case the fee amount is rounded up to the nearest calculable amount.
Hypothetically, your order can be filled with a huge amount of such low-volume trades. For every such trade, you pay slightly more than your current fee, and the total fee amount grows proportionally really high. But this is the worst-case scenario, which our system takes into consideration while calculating the total fee amount.
What happens in real life then?
As you create your order, the displayed fee amount is reserved on your trading account balance to pay the fees when necessary. Once your order is filled or canceled, the unspent amount is just unlocked, so you can use it again.
So what you pay in reality does not ever exceed your current fee rate. The alarming fee amount displayed is just a boundary effect, which only applies to very cheap coins.
Read more about HitBTC fees, which are in fact among the lowest on the market.