But there's a huge difference between being an established PL striker and one whose barely kicked a ball in the past 12 months. I imagine Robson-Kanu is on around £20k per week, whereas Rondon is on closer to £60k. It doesn't mean Berahino is worthy of a £60k p/w wage because he's played in the Premier League. As of now he has to prove he's still got the ability worthy of the deal.
Again, I didn't mention anything about being an established premier league player at all, or a proven striker, or anything like that. However comparing to Rondon who's on 60k as you suggest, Berahino has played more games (double in fact) in the premier league (106) to Rondon's 51, and scored more goals in the Premier League (23) to Rondon's 16. Could argue that he's more established? No one is saying he's worth 60k a week, I was pointing out that I believe if he signs for another premier league team he'll be on at least 60k. In fact he'll probably be on at least that if he goes abroad too.
Just as an aside, Fabio Borini, Danny Ings, Shinji Okasaki, Christian Benteke, Andy Carrol, Mbokani, Llorente, and many other strikers are all on £60k per week or more.