Well Füllkrug, Igor Thiago, and Evanilson were the top scorers for Dortmund, Brugge and Porto respectively. These are proper UCL clubs who regularly make the 2nd round and have appeared in Finals.
They were signed by West Ham, Brentford and Bournemouth, three teams with realistically no chance of earning a CL place. So there is a huge disparity in spending power.
This past window, Crystal Palace spent more than all 20 La Liga clubs combined.