Like for like will never happen.
But, let's take a random example. Let's say they spend around £12M and get someone like, I don't know, Dan Sturridge. First season, 14 appearances, 10 goals, 4 assists. Second season, 29 appearances, 21 goals.
No player is irreplaceable. Suarez is absolutely top class, but its not as if Liverpool are surrounded by sh*t or couldn't attract the best players in the world. To suggest otherwise would be monumentally stupid.