These "free" installers are frequently disguised malware that can harvest personal data, record keystrokes, or lock your computer for ransom.
Sites selling Office keys for $10–$20 are usually selling unauthorized volume licenses that Microsoft will eventually blacklist, leaving you with non-functional software. Community Warning
« Fake Microsoft Office site - First results on Bing when trying to go to... I hate that scam websites are often at the top of Google and Bing search results. » Reddit · r/Scams