By selling into multiple economies exporters reduce their market risk. With lower market risk and stronger margins they tend to enjoy higher valuation multiples.
Consider two similar companies with identical revenues, however, one exports while the other doesn’t. The exporter enjoys higher margins that yield a higher EBITDA. When the higher multiple is applied to the higher EBITDA, then the relative valuation of the company goes up significantly, by 50% in our example. For the same revenue sized company, the exporter is much more valuable.