Prior to joining Frankfurt, Haller was signed by FC Utrecht for just 750,000 euros (£678,000) from French Ligue 2 club AJ Auxerre, the Dutch club later sold the striker to Eintracht Frankfurt for 7 million euros (£6.3m)
As part of that sale, FC Utrecht carved out a sell-on clause with the Bundesliga club.
Should West Ham end up paying the full 50 million euros (£45.2m) which includes add-ons Telegraaf claim that FC Utrecht will net another 4 million euros (£3.6m) from Haller.
That they claim would make Haller FC Utrecht’s “best ever deal”