To be fair, "multi-" here typically means "dual-", but even w/o going to Alibaba, they're definitely out there:

  - http://www.androidauthority.com/best-dual-sim-android-phones-529470/

When I had to travel a lot, I had a small booklet of sim-cards that I could pop into my single-SIM phone (this was the 90s), in most regions I visited to get (much) cheaper rates than I was getting for world-wide roaming from AT&T at the time (this was before AT&T was really Southwestern Bell). Except Japan. (Curse you, and your island-nation cell-phone local-only standards, Japan!)

Heh, I'd disagree. I picked up a dual-sim Windows phone, unlocked, for $150 at the Microsoft store.

I've already taken advantage of it being unlocked by switching carriers (saved some bucks) when I saw the prices on one were now better than what I'd been paying.

Well, of course it's hard to come by a dual-sim iPhone. You need to look for other brands.