re: Walmart sells the AT&T Gophone for a low price!
Really enjoying the new 640 I picked up. I already had one, but when I upgraded to W10M on it, I found it was more responsive and less buggy than what I already had on W10M on my existing 640. I noticed I had a few apps that were "hung" and unable to properly install, so I think one of my Fast Ring updates went bad, and I had never reset it. After restoring to my new phone and running with it, I used WDRT and flashed back to 8.1 on my old one, then re-upped to W10M Fast Ring. Now they are both doing great. Never would have thought of doing that otherwise.
When I bought my tempered glass screen protector for my first one a while back, they sent 2 by mistake. I already had the spare one ready to go when I picked it up. Makes it an even nicer deal for me. Got a new case on the way, now I'll have 2 full-functioning phones ready to go. I'm real happy with that.
This doesn't really answer your question as to why, but almost everything is cheaper in the US, not just phones. For example, right now the average price of gasoline is about $1.77/gallon, which converts to about 0.42 euro/liter.
Yeah, I just paid $0.59/gallon this morning for 35 gallons of gasoline, filling up both my car and my wife's. It was actually $1.49/gallon, and I had a $0.90 per gallon discount code as a loyalty customer. Man, that felt so good. Max was 35 gallons, so we ran out both tanks and took in both cars for a fill-up. Gotta love it.