Ok, so the day Luigi released almost all stores got 20 Luigi's according to the DCPI tracker. Assuming Rosalina as a exclusive is NOT extremely rare, we can assume it should have around that number. Enough for people going to the store at opening if we are assuming they buy between 1 and 4 of them, since most likely there is going to be 3 to 6 in the shelf and the rest in the back.
If its rare, we can expect 4 figures per store,,,
So, in any scenario Rosalina shouldn't last more than 2 days, unless Target gets constant shipments. The fact that Rosalina is exclusive only in NA but not anywhere else means they are been produced as much as other characters. There is also the fact that is both a Mario character and a Popular character too.
All things said, I think its fair that people hunting for them should be able to beat scalpers and get one.
Oh, and has target ever enforced a one per costumer rule in-store? Just curious.