hearts are for 1 mil per piece on the dark market, but they die as soon as they leave the body so they become worthless. if you can find a way to keep the heart alive, then yeah that would work but most of the time it doesn't

kidneys, on the other hand, are worth 200k each and they can be kept for hours if kept cool. livers are worth 500k each.

you will have to keep her hostage until all the buyers are there then do the surgery then so there's no possibility that the organs will die under your watch