It is a large sum of money and is over the odds, but there is little risk to LFC, the only risk being he gets a career ending injury.
LFC sold Torres who was earning ?110K per week, for ?50 million, and they also sold Babel for ?6 million. With that money they bought Carroll for ?35 million as well as Suarez for ?23 million. The combined wage of these two will not be much more and could even be less than what both Babel and Torres was earning.
Torres could flop at Chelsea and because of his age he will not have any sell on value, so Chelsea are taking a huge risk with him. LFC however are just using the exact same money they got in for 2 players to buy 2 more players which do make LFC a better team, LFC have only spent ?2 million for these 2 transfers. Carroll has the potential to become a very good player and could justify his price tag, but if he doesn't he is still a low risk buy. If carroll flops at LFC, the club could sell him on for say ?20 million easily and then he has only cost ?15 million, which isn't a huge amount in football these days.