Originally Posted by ZeroZet

Thing is, they are not. These are premium packs, offering you their rarest commodities. You can't really expect a restaurant to serve you a full-course gourmet meal for a couple of bucks, after all.
And they already have "micro" parts in place, allowing you to draw Premium and one of Limited gachas for a mere 1$, once in awhile, and 3$ after that. And even regular draw prices outside of a free gems are not that big at 5$ when you exhaust discounted pulls.

^ This. It's been established numerous times there is zero NEED for a 6* (or even a 5*) to clear all game content, so the 6*s, and to a much lesser extent gacha 5*s, are purely premium content/bonus content. Furthermore, nearly all the games you mentioned make a huge portion of their money from subscriptions, something Nutaku does not have. Without that subscription money, the store for premium content must inevitably be more expensive (granted, as a portal/part-time developer its costs aren't in the same league as subscription-based MMOs).

Theoretically, you could make an argument that due to much lower costs, the subscription point is invalid, looking purely at the premium store prices. "Micro transactions" are designed to make you spend a little here, a little there, over and over. This is a LIMITED TIME OFFER, thus the whole point is "spend a lot now for an extremely rare item (in this case, a girl lol)" and thus cannot be fairly compared to the "micro transactions" that permeate many online games' daily offerings. As ZeroZet pointed out, this game DOES have its own micro transactions, and this is not by any means intended to be in the same category as them.