The latest fascinating research from the CIES Football Observatory has which players have brought their cubs the greatest 'transfer benefits' by comparing current transfer values to the fee that was originally paid for them.
And what has been revealed is that Tottenham Hotspur could potentially land a bigger profit if they were to sell talisman Harry Kane, now genuinely among the world's best players, than Barcelona would get if they were to cash in on five-time Ballon d'Or winner Lionel Messi.
Given that both players cost their club nothing as a result of being trained by the respective academies, it comes down to transfer value, calculated by a CIES Football Observatory algorithm taking into account variables such as performance, age and contract length.
Kane's value is €198m (£174m), while Messi is valued at €197m.
Another Tottenham player is third on the list, with the club paying a minimal fee to sign him from MK Dons as a teenager in 2015 and reaping the rewards of his soaring value. The difference between his current value (€171m) and his fee (€7m) is a huge €164m.
Atletico Madrid splashed out a sizeable €30m fee on Antoine Griezmann, but his transfer value has also soared to €158m as a result of his development and so the difference is worth €128m.
Paulo Dybala at Juventus has seen an increase of €115m since being bought for €40m in 2016, while Mohamed Salah is already worth a stunning €113m more than Liverpool paid to buy him from Roma just nine short months ago.
Marcus Rashford (€112m), Lorenzo Insigne (€105m), Robert Lewandowski (€102m) and Saul Niguez (€101m) complete the top 10 after all being secured by their current clubs for no fee - Lewandowski joined Bayern Munich as a free agent, but the other three were all home-grown.
Manchester City have been justified in paying big fees for both Leroy Sane and Kevin de Bruyne because each player is now worth €99m and €96m more than they paid respectively.
Now worth €83m more than what Barcelona initially paid for him, Marc-Andre ter Stegen is surprisingly the only goalkeeper in the top 20. That may be as a result of Thibaut Courtois and David de Gea both having shorter contracts which have hurt their transfer value.
The presence of Christian Eriksen and Eric Dier, both of whom were bought for minimal fees and have become highly valued stars, makes Tottenham the most represented club in the top 20.
CIES Football Observatory Top 20 'Transfer Benefits'
|Player||Fee Paid||Current Value||Difference|
|Harry Kane (Tottenham)||€0||€198m||+ €198m|
|Lionel Messi (Barcelona)||€0||€197m||+ €197m|
|Dele Alli (Tottenham)||€0||€171m||+ €164m|
|Antoine Griezmann (Atletico)||€30m||€158m||+ €128m|
|Paulo Dybala (Juventus)||€40m||€155m||+ €115m|
|Mohamed Salah (Liverpool)||€50m||€163m||+ €113m|
|Marcus Rashford (Man Utd)||€0||€112m||+ €112m|
|Lorenzo Insigne (Napoli)||€0||€105m||+ €105m|
|Robert Lewandowski (Bayern)||€0||€102m||+ €102m|
|Saul Niguez (Atletico)||€0||€101m||+ €101m|
|Leroy Sane (Man City)||€52m||€151m||+ €99m|
|Kevin de Bruyne (Man City)||€80m||€176m||+ €96m|
|Koke (Atletico)||€0||€88m||+ €88m|
|Eric Dier (Tottenham)||€5m||€93m||+ €88m|
|Christian Eriksen (Tottenham)||€13m||€100m||+ €87m|
|Mauro Icardi (Inter)||€13m||€97m||+ €84m|
|Marc-Andre ter Stegen (Barcelona)||€12m||€95m||+ €83m|
|Ciro Immobile (Lazio)||€9m||€88m||+ €79m|
|Eden Hazard (Chelsea)||€40m||€118m||+ €78m|
|Dries Mertens (Napoli)||€10m||€87m||+ €77m|