Is it ok in this situation to ask a person at what price she sold something to another person?

I am a dairy goat farmer. I recently acquired a guardian llama to protect the goats (yes, this is a real thing). When she came over, her guarding instinct (which can vary widely in individual llamas) had not yet been tested, plus her owner was still thinking of breeding her, so the agreement was that she would be on loan to me for the time being. Now, the owner has decided against breeding, and the llama, Maxine, has proven herself a very worthy protector and a valuable addition to the herd – so the time has come to transfer ownership. The problem is, I asked what I could pay my friend for her and her response was, No cost; it’s not about the money when it comes to animals. I understand this feeling because I love my animals too, but I also know she is a farmer who makes her living off working with her livestock, and that’s not much of an income. So I very much want to pay her at least in trade (will be in labor, piglets, and goat kids), but I need an idea of what she paid for Maxine.

I’m guessing it could have been anywhere from about $400–1200 – llamas vary in price quite a lot, and the person who sold Maxine to my friend is an unscrupulous dealer who sometimes overcharges. But I happen to be acquainted with said unscrupulous dealer, and so I am wondering if etiquitte might allow the question about what my friend paid her. I honestly have no idea – never felt the need to pry into others’ private transactions before. Thoughts?