It can't last, says Trainer. He predicts that fees for trading cryptocurrencies will follow a similar downward trajectory as those in stocks, possibly all the way to zero. Coinbase's slice of each transaction is so big, and its profits so gigantic, that rivals can slash what they're charging and still mint huge profits. "Competitors such as Gemini, Bitstamp, Kraken, Binance, and others will likely lower or zero trading fees to take market share," he says. "If margins are that good, you invite competition." That will start a "race to the bottom" similar to the contest for market share that triggered the collapse, then virtual elimination, of stock commissions in 2019. Trainer also expects traditional brokerages to soon offer trading in cryptocurrencies, further pressuring Coinbase's rich fees.