Across almost every market, the smaller and less traded an instrument is, the more it costs to trade. Crypto follows the rule closely. The gap between the cheapest and most expensive coins on a venue can be wide, and it comes from the same few causes each time.
Someone takes the other side
When you buy at once, someone sells to you at once. That someone is usually a market maker, a firm whose business is to quote both sides and earn the gap between them. Having sold to you, it holds a position it did not want. It has to find a buyer or hedge the position, and until it does, it carries the risk of the price moving.
The spread is the maker’s payment for that risk. So the cost of trading a coin is mostly a statement about how hard the maker’s job is. The bid-ask spread explained covers the general case.
Depth
On a heavily traded coin the maker can pass the position on within moments, because other orders arrive constantly. On a small coin the next order might be minutes away. The longer the wait, the greater the risk, and the wider the quote has to be to cover it. A thin book also means a moderate order moves the price, which adds to the cost for anyone trading more than a small amount. Reading order book depth shows what thin looks like.
Volatility
Small coins tend to move more. A maker holding a volatile coin for a minute takes more risk than one holding a calm coin for the same minute. Higher volatility widens spreads on any instrument, and small coins usually have both problems at once: slower turnover and larger swings.
Fewer makers
Competition narrows spreads. A large coin attracts many firms quoting against each other, and each one has to stay tight to win orders. A small coin may have only a few. With less competition, nothing forces the quote narrower than is comfortable for the firms making it.
What this means for the trade
The higher cost is not a penalty and nobody is being unfair. It is the going price of immediacy in a market where immediacy is scarce. But it does change the arithmetic. A small coin has to move further to cover its round trip, and the exit often costs more than the entry because exits tend to come when everyone wants the same side. Why exits cost more than entries on thin pools covers the on-chain version of that.
The cost can also change. A coin that becomes heavily traded gets cheaper, and one that falls out of favor gets dearer. A figure read last month may not be today’s figure.
Where to see it per coin
The NoVo Crypto Market Map ranks what a round trip costs on each coin from Robinhood’s own disclosed markup, so the spread between large and small coins is visible in one list. The same map shows on-chain tokens by pooled depth, which is the other half of the picture for coins that trade in pools.