Liverpool haven't signed Mascherano permanently. Yet. Rafa has said that a deal could be made in a few days, though.
Liverpool fans seem split down the middle as to whether Mascherano is worth £18m or not. Some were threatening to assassinate the owners if they didn't make the money available, some were saying that he's overrated and the money would be better spent elsewhere.
It might seem ridiculous to spend £18m on players like Mascherano and Hargreaves, but on their day they can be just as important as the Torres's and Ronaldo's. If Hargreaves makes us harder to beat in Europe, he's well worth every penny.