I'm amazed that anyone is still surprised or unaware that Cryptic, especially under their new owners, is going to do whatever they can to get you to buy dilithium from them for cash. (Indirectly, perhaps, but the exchange merely adds a step.)
NEWSFLASH: Yes, they want your money. All of it.
NEWSFLASH NEWSFLASH: All companies share the same mentality. Cryptic isn't any different.
While the cost of 100 more DOFFs /is/ kind of high, I don't see any reason why you need 400 total. I could see myself maybe buying a single +100. Maybe. And I only "main" two characters or so.