[Swamp Yankee]

If you're looking for American made, the lowest price I can think of is around $400 for the Sailor brand ukes. They're only available at Uke Republic.
Just north of that are the Loprinzis. In fact, the rumor is that Sailors are made by Loprinzi. I see a lot of love for Loprinzis out there, though I don't own one. Uke Republic for them as well.

Martin's entry and intermediate ukes are Mexican made. I don't think they have anything under $1000 that's American. I have played a few of their Mexican ukes and I didn't see why so many others rate them so highly.... but lots of people love them.

I have a ca. 1947 Martin concert ukulele and I can certainly understand the enthusiasm for vintage Martins... but I'm not thrilled with their Mexican ukes that I've played.

Then there are the Hawaiian makers: Koaloha, Kanile'a, Kamaka, Koolau.. You're lucky to find one made in Hawaii for less than $800. Some of them have lower priced Asian made models though.. Each have their followers, each are highly rated by uke enthusiasts. The Ukulele Site has lots of them as well as excellent videos of the ukes being played.

Kala, which mostly offers Asian made ukes, has the Kala Elite series, which are American made. I don't know much about them but they start at around $500 new.

Personally, I am very partial to Japanese made Kiwaya ukes. Four of my favorite ukes, out of 16 total, are Kiwayas. Their tone, playability and build quality are top notch. I think they're well worth their prices, even a bargain, considering the quality.