Here's the full text fwrend referred to:
"Multiple versions to suit all needs
T-RackS 5 comes in different packages so you can choose the best option for your needs.
Previous users, owning some or all modules, can go straight to T-RackS 5 and take advantages of all the new features. This version is also ideal for beginners or users getting into mastering for the first time since it includes the 4 new modules along with 5 additional classic T-RackS modules (for a total of 9 processors) to jump-start things right away and let you mix and master taking advantage of the finest analog modeling technology and classic sound that we are known for.
For more demanding users T-RackS 5 Deluxe offers 22 smartly selected modules that cover you for most mixing and mastering duties with a wide selection must-have vintage and modern EQs, Dynamics processors and more.
In each of this version you are always free to add more modules as time goes by, thanks to the exclusive T-RackS Custom Shop, that allows you to try any of the available processors for 14 days, and buy them a-la-carte using $/€ or Custom Shop credits for greater savings.
If you want the full processing power of the entire suite at once, T-RackS 5 MAX is the full-blown collection of all 38 available T-RackS processors covering everything from vintage compressors and EQ’s to reverbs, stereo processors, saturators, precision digital tools and more."
Third paragraph puts it clearly: you only need the basic package at $99 to upgrade all you have and get the new engine as well as the four new plugins that come with it.