I have 2 b's that I got as adults from Pam…Ruby and Brando (technically a foster). Both came on a 30 day trial to see that they fit into my home situation. Both are really bonded to me and my family...I don't remember it taking any time for that to happen. Ruby was a little skittish around my brother (he is 6'5"...so I think she had never seen someone his size) for the first month she was here...now she jumps up in his lap when she needs to get away from Brando :D. I added a b puppy to the mix about a month ago. To me, there is no difference to me as to how Aaliyah (pup) has bonded with me, vs. how Ruby & Brando bonded with me.
Money wise, I'll spend a lot more on the puppy than I will have on the adults because they came to me with all of the testing already done. Initial cost of pup, puppy shot vet visits, obedience training, (in my case, show handling classes), wellness exams, CERF, hips, patellas. Now with Brando & Ruby (because they have been bred), I will still have CERF, thyroid and wellness done, but in general, I think an adult costs less than a puppy until they become seniors.
I too think the price is fair. Because I know Pam & Sheila well and visit with them often, I know what they put into their dogs and all the testing that they do. I'm really amazed at it all...and the money they put in. All you have to do is look at the OFA site and put in Eldorado and you see all the testing they do.
Based on what you wrote, I think they are having a friend of theirs finish Dillon and then he'll be available as a pet.