But isn't the sat 5 way more expensive? Isn't that the reason why his new rocked is so good?
The new rocket is so good because you can use it over and over again.
A Saturn 5 contains a million components and is a single use vehicle. You bring together a million bits and its over in one flight. You may as well blow the thing to bits on the launch pad, the result, for the vehicle, is the same. You can't use it again.
The Heavy brings together a million bits and it lands itself back on the ground once it has pushed something into space. Of the million bits you can use something like 750,000 of them again next flight. Makes the next flight cheaper as 3/4ths of the manufacturing work has already been done.
The Space Shuttle with its reusable boosters and orbiter was supposed to be a reusable solution that would make space travel cheaper turned out to be good, but not as good as once hoped and was retired.
The only down side of the current SpaceX rocket system I can see is it uses rocket power to land. That means it has to take its landing fuel up to separation stage and use it to come back down again. When escaping Earths gravity well that weight means something, but obviously thats been taken into account and deemed acceptable.