Heh, if it wasn't for the actual value of the book (but probably only for divine heroes) they'd still have been scammed.
"200 gold, but 100 gold since I need a quick deal."
[Counteroffer, 3 silver.]
"10 gold, else I'll operate on a deficit."
[Counteroffer, 4 silver.]
"Ok, 1 gold, but then you have to take the rest of the trash as well so I can tell my big bro I sold everything." (And then he can brag for his brother how well he did, since on average he got more than a silver per item.)
@Kaarme - Or even before he went to sleep. Only excuse might be that since she was so interested he might want to keep it around for her "plan" first instead of "losing" it (and getting a "clumsy" label) or revealing his special ability to learn.