The link you've posted to includes several deliberate misrepresentations (aka lies) about the nature of the product (i.e., claiming it is cashmere when it's just cotton-polyester).
In LA's fashion district I can find you a locally made cotton-polyester sweater for under $10, and the seamstress is making a living at that price and using quality cotton-polyester fibers rather than the scratchy cheap QA-rejects. I could probably even find an actual cashmere sweater for under $50, made out of cashmere wool.
The trick you're using is that Alibaba is essentially a wholesaler and most non-boutique US wholesalers don't list prices on their websites because bulk customers negotiate. I can't even find one that lists wholesale prices for that kind of sweaters.
You're also both times looking at sources direct from China, which are taking advantage of that Universal Postal Union treaty situation that makes it cheaper to ship from China to the US than to ship within the US. If they were paying market rates for shipping the shipping from China would itself be more than $2.90. Notice how similar sweaters on Amazon end up being closer to the price of the made in USA one (or more) even when they're made in China, because then they're being shipped from within the US. (This is also why comparing wholesale prices is more relevant; the "free shipping" that gets incorporated into the price is less of the total.)
And it's difficult to even find non-boutique apparel made in the US at this point, because most of the ones that try to compete on price rather than status then lose to China on price by a small percentage and go out of business. But the boutique prices don't represent what it actually costs to manufacture in the US, they're just the ones who can stay in business in the US.
You won't easily find one after the manufacturing base has already been gutted. It's too late to look now except for the higher priced boutique items that still exist.
In LA's fashion district I can find you a locally made cotton-polyester sweater for under $10, and the seamstress is making a living at that price and using quality cotton-polyester fibers rather than the scratchy cheap QA-rejects. I could probably even find an actual cashmere sweater for under $50, made out of cashmere wool.