Reports in the north east claimed the Magpies snapped up Merino for a 'cut-price' £7million when Rafa Benitez moved quickly to turn the 21-year-old's loan deal into a permanent transfer in October.
But Dortmund sporting director Zorc believes his club were more than happy to almost triple their investment in the Spaniard who cost them 3.75million euros from Osasuna the year before.
Merino never made it into the first team at the Bundesliga club, leaving on a season-long loan deal that cost the Magpies three million euros to set up last summer.
And when Newcastle agreed to stump up another seven million just a few months later, Dortmund were delighted, and the Germans believe they can profit even further from any resale in the future.
Zorc said: "If we take the case of Merino, who was transferred to Newcastle United via a loan with a compulsory purchase option with relatively little risk, then one has to say ultimately, that was a good business for BVB.
"In addition, we continue to participate in his future development. In other words, should he be able to penetrate elsewhere, BVB will continue to do so. If it works like this, I cannot find much negative about such a transfer because not everyone can do it with us."