  A large number of Data Marketplaces (DMs) have appeared in the last few years
to help owners monetise their data, and data buyers fuel their marketing
process, train their ML models, and perform other data-driven decision
processes. In this paper, we present a first of its kind measurement study of
the growing DM ecosystem and shed light on several totally unknown facts about
it. For example, we show that the median price of live data products sold under
a subscription model is around US\$1,400 per month. For one-off purchases of
static data, the median price is around US\$2,200. We analyse the prices of
different categories of data and show that products about telecommunications,
manufacturing, automotive, and gaming command the highest prices. We also
develop classifiers for comparing prices across different DMs as well as a
regression analysis for revealing features that correlate with data product
prices.
