As to why they're cheaper than internal drives, I doubt we're getting something for nothing and I also doubt the manufacturers wouldn't drop the prices on the bare drives if they could. It may be the external drives are ones that failed the quality assurance needed for internal bare drives while still being functional, so I wouldn't bet that a salvaged external drive could be trusted in heavier use.
What do you think about the wd re4 2tb from eBay?
And they are less popular for the other 10-11 months out of a year...why, exactly? Do people give them as gifts, now (and if so, why didn't I get any for Christmas? I could use extras! 😀)? They tend to be occasionally cheaper, but are usually more expensive.External drives are more popular, therefore they cost less.
Such misinformation...
External drives are more popular, therefore they cost less. It has nothing to do with quality.