The really cheap stuff actually doesn't even have a power supply! There's a breed of LEDs that takes straight AC and rectifies it using the LEDs themselves. By using a large number of tiny LEDs in series (typically in COB form), you can easily reach close to 110v or even 220v, and then you add a small current limiting controller in series that's dirt cheap compared to magnetics... These are super cheap, and appear bright, but they flicker at 120hz, which can be annoying when there's motion or if you're sensitive to it.

I'd say it's a very bad choice for a bedroom or living room light, but I have nothing against it for the outdoor lights, signage and a bunch of other applications where cost is king.