Re: Office - that deal that Jon linked to seems to still be active and it's definitely cheap.
Please do understand though that these aren't straight up legit keys - they're what's known as "grey market" - ie: they're keys that were intended for a particular product channel - usually either the Microsoft Software Developer Network (MSDN) or TechNet for IT Professionals who pay a subscription fee - mostly intended for evaluation purposes. Or they're left over from a bulk buy of OEM licenses. Many of them will work - some won't. Some may work for a while and then stop working. And you almost certainly won't get any assistance from MS if you need it, as the thing with OEM licenses is that there is no support from the developer (support is supposed to come from the vendor - and that won't happen with these discounted ones sold online, because, of course, the OEM software is not supposed to be sold separately from the machine.) Anyway - as long as you are aware of all that and ok with it, then fine. One would hope that the deal being promoted by AppleInsider is one of the more reliable ones, but no way to tell. Also no way to tell if the key is US-specific, btw. (this is definitely an issue with keys intended for non-North American markets - I'm just not sure if they differentiate between Canada and the US as well for the perpetual licenses - they most definitely do for MS 365)
I now use MS 365 - it has a few useful perks that you don't get with perpetual licenses: software is continually updated, and you get 1TB of online storage per user with OneDrive. As I noted above: MS 365 is region/country specific - a 3rd party key bought in the US will not work in Canada. If you were to try to buy at MS 365 in the US from Microsoft directly, it will switch you to the Canadian site/pricing.