Tower of the Golden Order x2

[Edi]

The price is more than justified, since the only one with even remotely as big a research bonus is a lore master, and the metal order adepts are cheaper yet have almost as much research since they have more base paths.

Just FYI, there are three versions of each metal order tower and each gives a different gem income. They are 2+2, 2+3 and 3+2 wrt the primary and secondary gem incomes, plus lab plus allows recruiting the mages.