Dark Tower Revised help

[Sousa89]

I'm starting to get into this series but I've noticed that on amazon they have revised and expanded editions which confuse me. It says 3 and 4 are being revised and expanded(at 9.99) but they have another version of the same books(at 14.99) that were already revised.Since Stephen King is meant to revise the older books in order to continue with the more recent books, does anyone know what the differences are? The more expensive ones were revised a few years ago but since there being revised again should I wait or are they just the same?

I'm pretty confused lol

 

[Sousa89]

Anybody? I can't find an answer anywhere haha

 

[Peder]

Have patience. It is hard to beleive that someone of the many King fans around here couldn't provide some help.