AmpliTube 4 contains quite a lot of gear. You can see what is included at
https://www.ikmultimedia.com/product...dex.php?p=gear
You get 10 stompboxes, 9 amplifiers, 10 cabinets, 29 vintage and modern individual speaker models, 4 microphones, 2 rack effects units, 2 tuners.
The reason some presets have gear included that are not with the base AmpliTube 4 package is so you have the ability to demo that gear (which you can do easily by opening Custom Shop and clicking the "Try" button next to the gear).
You may want to take a look at
https://www.ikmultimedia.com/products/at4max to compare the gear there vs purchasing via the Group Buy but the latter is definitely an amazing way to get a TON of gear.