Are MIL and her sister hoarders? Did they grow up poor? Both sound like they have a very unhealthy obsession with "stuff" and bargain-hunting/saving money.
Oh they do have a borderline disorder with their bargain-hunting activities. They grew up in a very large family. While they were not poor, they were the poorest family in a . very wealthy neighborhood. They are crazy frugal and love finding bargains. Its a game to them. One of their brothers who lives further away is a classic hoarder. He has a house that is falling apart in a very low cost area with a good amount of land around him. He searches for free things and builds storage shanties himself on his property. Its terrifying and looks like a junk yard.
I'm not giving her $100 for a broken toy that she insisted we take. We know not to take anything else. I'll let DH go with the flood story if he wants to do this.