How much to sell my Becco Butterfly?

I bought it in 2007 and I used it for a year. After that, I lent it to a friend who has had it since (she used a few months). She wants to buy it off of me. I don't remember what model it is; I think it had whatever safety retrofit it needed too. I have 0 idea what a fair price is for her to buy it from me for. I haven't seen it in so long! Thinking $50 minimum but maybe I should ask for more?

Beco has discontinued the Butterfly, so you might have great luck pricing it higher despite its age because of that.

Poke around the babywearing scene to see how much they're currently selling for used.