On the way back to Dalaran, Rex watched Kael'thas, who was deep in thought, with great satisfaction. Dalaran stood clearly in view ahead of them. Back at Back Mountain, Rex had reached an agreement with Kael'thas, trading the Arcane Tower blueprints for one hundred thousand gold coins in cash and a large quantity of magical materials. Building an Arcane Tower cost ten thousand gold coins, but that was in Gilneas. For the High Elves, the expense would be far lower. They already possessed most of the magical materials and could save a considerable amount of gold. Rex had taken precisely this into account, which was why he had later asked for magical materials rather than more gold. To be fair, the goods the High Elves sold tended to be rather overpriced.
This time, after examining the Arcane Tower blueprints, Kael'thas had been quite generous. The magical materials he offered satisfied Rex; otherwise, the blueprints could never have sold for a mere hundred thousand gold coins. They were nothing like a Hearthstone. Rex had gouged Kael'thas for ten thousand gold coins for just one Hearthstone, and the Arcane Tower blueprints were far more important than a Return Scroll. More importantly, these were blueprints, which allowed the buyer to build the towers himself.
That was also why Kael'thas had suspected Rex of having another motive the moment he saw them. Anyone with something like this would normally keep it hidden and retain sole possession of the blueprints.
Rex had made careful calculations. The magical materials he had specifically requested from Kael'thas were all essential to building Arcane Towers, while the rest could be found within Gilneas. When Kael'thas calculated the price of those magical materials, he had used their cost price throughout. Perhaps seeing Rex offer something as valuable as the Arcane