The finishing positions tend to correspond most closely with the amount spent on wages rather than the amount spent on transfers (although the two are not unrelated) - paying existing, proven players more money to keep them at the club tends to be a much better use of money than splashing out on...
Of the players no longer at the club, they lost money on all of them apart from Modric...
2 Roberto Soldado £25.50m - 10m (15.5m loss)
5 Darren Bent £21.04m - 16.5m (4.5m loss)
7 David Bentley £18.70m - released (18.7m loss)
8 Luka Modric £17.85m - 30m (12.15 m gain)
9 Paulinho £16.77m - 9.9m...
Interesting article in the Observer that says that Spurs buy particularly badly when they splash the cash...although they certainly sell well.
https://www.theguardian.com/football/blog/2017/jul/22/dele-alli-harry-kane-tottenham-football-silly-season
This is a list of their top 12 all time...