RIPE Labs on their view of the IPv4 transfer market:

In the second half of 2015 and the first half of 2016, both the number of transfers and the size of the transfers conducted under RIPE Policy started to show a downward trend. This is more likely a sign of fewer available addresses rather than decreasing demand for IPv4 addresses. Also, we have to stress that statistics for IPv4 transfers within the RIPE NCC service region only concern address space with the status Allocated PA or Assigned PI. Because legacy space is not subject to the RIPE transfer policies, the RIPE NCC cannot track or publish transfers in this area. Inter-RIR transfers are still too small in number to see any trend. In terms of the number of transferred IPv4 addresses, statistics are dominated by a single transaction, eight /14s transferred from ARIN to the RIPE NCC in December 2015.