This is an interesting one. I've been using this 'cheap' - i.e. under ten quid - copy of MS Office 2016 for a couple of years. Bought off ebay and downloaded quickly and efficiently. No comebacks whatsoever.
**However** I've just downloaded a couple of copies of '2019'. Again successfully, but I notice that within 24 hours ebay has taken the offers down. Are Microsoft mounting a campaign against these cheap sellers? I suspect that they might be.
But in conclusion, I've not paid full price for software for years; never knowingly bought 'bent' stuff; never had a failure yet...
Oh dear... what have I done?