Question

How can there be any economic gains for a country from both importing and exporting the same good, like cars?

Short answer

There can be economic gains for intra industry trade, based on specialisation & economies of scale, as per Krugman Model.

Step-by-step solution

Intra Industry Trade Definition

It refers to international trade of goods from the same industry.

Eg : Many developed rich countries both produce & export autos, and also import autos.

Economic Gain concept

Economic Gain is the gain in efficiency & social product, utility.

Intra Industry trade leads to economic gains in countries with similar economic welfare levels, in following ways as explained by Krugman New Trade Theory

• Division and specialisation of labor : because labor is deeply imbibed in diligent small portions of work processes, related to production of a well defined good.
• Economies of Scale : because a brand's standardised production is likely to be concentrated at one location with huge quantities' production.