Hello wizard
Welcome to the forum.
You have to remember when ranges are given out for replacement notes, this is only how many are possibley avaliable. That does not mean there are that many out there. So you can have and 80k range and only a few of the notes avaliable and a 40k range out there and hundred out there.
It also goes on supply and demand also. If you have 400 replacement collectors and only 50 notes, price increases
Try to buy the unc and better. These notes will increase probally the most or keep their value the longest. But remember, if there is a real rare note in vf or ef, have seen some go for a pretty penny.
Changeovers are the same but i am not sure how many people collect them. they are always nice to have because you see a total name change or design or year. Easily recognizable.
Happy Hunting
Polarbear