So we have sold Bebe? And i can ask the same question, you dont know the clause and no club will put a clause on 10 games or 2-3 goals.
Utd are closer to selling Bebe than Liverpool are Aquilani since Juve have actually withdrawn their interest.
And David Conn seems to suggest there weren't any add-on clauses. The 'clause' was the buy-out clause in his contract, which he signed a matter of days before signing for Utd. The release clause was £7.4M
Bebé played only six pre-season friendlies for Vitória, before stories began to circulate that he was attracting interest from some of Europe's top clubs.
Vitória then quickly put him on a second, improved contract, on an enhanced salary with a bigger buyout clause – the price any club would have to pay if they were to sign him – to €9m (£7.4m).
Bebé: Six steps that took a Lisbon street kid to Manchester United | David Conn | Football | The Guardian
EDIT:
Although, of course, most of that went to Jorge Mendes.