Sales areas to get more than say $50-60 for the set. Informed buyers will not pay more than the going rate of 20-25 for a used blowback. You're tanks might be hitting the 5 year mark as well, if so they are give seats as well. Finding a buyer may take some time, hit cl and the like.
I sold 4 similar blowbacks all in good shape for $100 last summer.