San Jose over paid... Kane was not going to get this kind of offer on the open market IMO. They are paying him with expectations that he continues the level of play he had with the brief time at the end of the season with them.
The guy is prone to injuries, is a locker room cancer and is very streaky. I'm not sure if the streaky part is from laziness or if he is not consistent. Last year he started off hot and then had 4 goals in his last 30 games with Buffalo before he was traded.
All the stars have to align with him staying out of trouble, staying healthy, playing at his peak level for this deal to work out.