The $100 Starfield Premium and $300 Constellation editions of Starfield allow you to play the game up to five days early, starting September 1 instead of September 6. But you don’t have to spend that much to jump in ahead of time.
Microsoft is also offering a $35 Premium Edition upgrade (or $31.50 if you have Game Pass) that includes the early access perk, as well as the Shattered Space story expansion (when it releases) and in-game items like the Equinox Laser Rifle and more. Players also get the Starfield digital art book and soundtrack.
The Premium edition upgrade does not come with Starfield’s base game itself, so it seems that this bundle is aimed at people who are planning to play Starfield through Xbox Game Pass. All of the Premium edition upgrade content requires the base game, so if your Game Pass subscription lapses, you’ll lose access to the game and its related content, it appears.