Clearly she needs to charge enough for the sweatshirt to at least cover costs, and she provided reasons why the costs here would justify that price.

She could charge less if she used sweatshop labor, but that would make her a hypocrite. The price she lists is in-line with her oft-stated political/moral beliefs.

Musk's point here--as best as I can understand it--was to claim that AOC was being a hypocrite.

Also it still costs less than a Tesla sweatshirt ($75)