A man in town has a large collection of mint condition Gregorian Chant LPs from various choirs for various feasts and liturgical seasons (at least 30 volumes). He said he is not trying to make any money from selling them, he just wants them to go to someone who will use them. He knows I'm the chant director at the Cathedral, and said that he will accept whatever I offer.

I don't have a lot of money, but I don't want to insult this generous man with a low bid. What should I offer for this collection?