Portuguese football is very different from the Premier League, the finances make sure of that. Although clubs such as Benfica, Sporting Lisbon and Porto can still afford to bring in talented players they often have the help of third party companies and investors, looking to make money on progressing talent. Often those investors can make more than the actual players, given the comparatively low wages in Portuguese football.
Sporting are concerned about the future of William Carvalho. They don't want to sell the young midfielder for less than his €45m buyout clause but they are also aware that if he feels he's being short changed he could push for an exit, and that disruption could bring the player's value down.
That Sporting have Carvalho on a clause as high as €45m would suggest they value him very highly but according to Portuguese newspaper O Jogo he's only currently paid about €3500 a week, which by British standards would be comparative to a lower league player. Sporting have given him bonuses this year but they are now ready to give him a pay rise to, drum roll please, €7000 a week.
The Portuguese club would keep him for a year and hope someone then paid closer to his clause, if that doesn't happen this summer. That a club can ask €45m for a player they only pay €3500 a week shows a side of football which certainly isn't weighted in favour of those who actually play it.
Manchester United have watched Carvalho repeatedly this season and clearly hold a level of interest. Despite the Sunday People jumping the gun, a recurring theme, in March and saying Manchester United had agreed a fee of £37m (the player's clause when converted), progress on any potential deal appears to have halted. That's led some to believe the interest was being driven by David Moyes.