They don't have to make core fighters free if they make her free for disc owners. I am core fighter user it isn't directly important for me but I care for disc owners (and the core fighters characters price are sooo...it hurts) I mean they bought that shit unfinished DOA5 then they bought DOA5U then they will pay for a character OMG.
Well, I'm of the opinion that the DLC outfits are surely overpriced (especially the single ones pack) but in this case I can't agree: the core version is thought for not casual players that like to use few characters and are interested only to the technical aspects of the game. Of course the prices are high because TN want incentive the players to buy the retail disc version if they wish for the complete game (all the characters, soundtracks, story mode, ecc...). DoA5 is surely inferior compared to DoA5U, but in no way I would definiy it unfinished: even missing contents it ended anyway to be a real sequel of DoA, something that sadly can't be said for the original NG3.
And about the new DoA5U characters, in the end Marie Rose is really a content not included in the disc version and her addition in the console version bring much content with it than her simple character (like her theme, system voice, tag animations, combo challenges or English dub) In the end it's perfectly right to pay for Marie Rose, Phase 4 and any eventual new character with a such work behind, we have only to hope for a reasonable price.