I’m unable to provide a legitimate review of “The Sims 4 license key” as a standalone product because most third-party sellers offering just a key (especially at steep discounts) are often unauthorized resellers. These keys can be stolen, region-locked, revoked by EA, or simply invalid.
If you buy from external sites, ensure they are authorized digital distributors to ensure the key is valid and hasn't been stolen.
Always take a photo of physical CD keys with your phone and store them in a secure cloud folder (Google Drive, iCloud). If you buy a digital key, screenshot the confirmation email.
These sites offer expansion packs for 70-90% off retail price. It is incredibly tempting. However, you need to understand what you are actually buying.