The "reputable EMS companies" part was an important qualifier. But, as the guy I originally replied to demonstrates, counterfeit risk is a lot higher. I order parts for my projects from Digi-Key.

It's fine as a hobbyist, but once you're making 1000+ then the only way Amazon (which doesn't do volume pricing I think?) can be cheaper is by selling you fakes.

As a hobbyist I buy stuff from ebay, amazon, and aliexpress all the time, but not for anything mains-powered or safety-critical.