9) Ajax, 2008 – €35m
Ajax didn’t spend a huge amount compared to some of the sprees on this list, but it’s a lot compared to their ususal outlay, and Dario Cvitanich, Olegeur, Evander Sno and Ismael Aissati all flopped, while their record signing from that summer, Miralem Sulejmani, recently left the club on a free transfer.