Jesus did not tell James and John that "Salvation is not easy"... not in this passage and not anywhere else.John and James believed that they were already saved because they were among the apostles.
However, the truth is that salvation was not easy, according to what the Lord Jesus told them.
Even though they were among the apostles, since salvation was not something easily attained, they still had to drink the cup that the Lord Jesus drank before they could be saved.
Instead of presenting your own ideas that have no basis in Scripture and treating them as Scripture, perhaps you should try starting with the literal text of Scripture and show word by word where you think Jesus said salvation is not easy.