Is this a reseal, as the footer looks like it might be missing? Or is that it standing upright on the right-hand side of the figure's legs; it's hard to be sure?! If it is a reseal, obviously that will massively affect the value.
As for figures debuting on cards that they themselves did not appear on the back of, I don't know the definitive answer, but I've always assumed it was probably because the new cardback artwork wasn't always available in time for the first run of figures in a new batch, and so it was simply easier to re-use the previous artwork until the new one was ready. I might be talking utter nonsense of course, as that is just my guess, so I am very happy to be corrected by anyone else with greater knowledge