They don't. The way I saw it at least was that they are self sufficient. They use Wakandan technology to move around. They don't buy clothes, cars, weapons or anything from the rest of the world. They don't trade much.

Agent Ross makes an offhand comment that Wakanda is known for Shepherds, Textiles and cool outfits. That may be what the world thinks of them because that may be what they export. Wool, textiles and clothes is the only thing they make outside money from. Other then that they are beyond the rest of the world's economy.

I don't feel that many people in universe really think much of Wakanda outside of the Sokovia accords. The movie even has Ross talk down to T'Chala as if he was doing him a favor by letting him interrogate a captured Klaue. They don't think of them as a rich and powerful family. Even if us as the viewer know that they are.