That’s a really high percentage. The market at the time may have influenced the contract. And the urgency.
@FatherTim, did she look for used books? Or look into renting? You do have to compare the exact ISBN number, which is the specified edition. And if it’s a new ISBN, you check to see why. Eg, in some cases, there’s a vital add or revision. It’s wacky, yes. But mine were able to rent what they needed.