In other words, dominance in a market, not aggregate GMV across many markets, is the goal of any marketplace and ultimately what determines equity value.
Uber is the quintessential example of a marketplace with low transaction complexity and asymmetry. Matching demand and supply is simply a function of availability and pickup time — commissions are the obvious fit here. On the other hand, marketplaces like Classpass and Scoutbee avoid commissions entirely.
For the marketplace to succeed, the value of convenience it provides must, therefore, continuously outweigh the monetary gain of moving off-platform (ie. not having to pay the commission the marketplace charges).
Derived products are rarely seen in marketplaces because this data is better used internally to improve matching on commission-based marketplaces or lead generation in paywalled marketplaces. In rare cases, marketplaces targeting complex and opaque markets, like Leaflink, can provide aggregated and anonymized market data as a part of a paid tier.
Service marketplaces must continuously provide value in terms of either discovery, convenience or trust. In line with this, successful service marketplaces tend to be either repeated-discovery, online-first or SaaS-enabled.