I guess one reason we can get the (almost) whole Library which is a very good deal is the abundance of litterate and available Eonir willing to scribe for the queen. So copying books might be cheaper for the Eonir than other polities. Might be preferable for the Queen over giving away valuable currency or trade goods that could be used elsewere.
Giving away the books to a reliable research partner in exchange for priceless relics is also a show of cooperation that goes beyond a simple commercial exchange into a truly strategic mutually benefitial exchange. Priceless relics for priceless knowledge, we both get out of this stronger at little cost. We give away scraps and the Eonir give away the time of their numerous idle litterate citizens. Win-Win!
Giving away the books to a reliable research partner in exchange for priceless relics is also a show of cooperation that goes beyond a simple commercial exchange into a truly strategic mutually benefitial exchange. Priceless relics for priceless knowledge, we both get out of this stronger at little cost. We give away scraps and the Eonir give away the time of their numerous idle litterate citizens. Win-Win!