The core of Mainland ukes are made in the far east, most likely in the same factory as a lot of other big brands are made. The difference in quality is that rather than have them finished in the far east and just shipped from there, they all go to Mike in the US who individually finishes and sets them up. Any that don't make the cut on the build (I finish flaws or not capable of holding a good setup ) are rejected.
As such, for the price, you stand a far far higher chance of getting a good instrument with Mainland than with some of the bigger brand names.
Now, that said, with the bigger brands, it depends where you buy from as a good store will also sort setup for you.
But anyway, Mainlands rock.