Romana reduces 8 powered cards to 7 power so that it takes 2 extra pills to beat her with junkz bonus. This is the advantage over mahimatah (who is also a very good card).
The reason she is so expensive doesn't have much to do with how good of a card she is.
Plus junkz are way more popular in dt and other modes than frozn.
romana has the junkz bonus (+ so extra 2+ pills are needed in most situations to overcome bonus
rare and uncommon is also important
price has also been manipulated. imo she should be less but i would recommend her as she is imo the best 3* for junkz (only other very good one is tremorh)