Welcome to the family TS, I bought a 2013 BH this year, I really have to guess at to what 2010 model should cost, but you can look around at some for sale ads all over the internet and get an idea of what that year model is selling for.
More importantly, when you do go check it out, have the salesman or a tech hook up all electrical and water systems and make sure everything is working properly. Especially the generator. It would be great if you could spend the night in it and slowly check things out for yourself.
Good luck, shopping is half the fun of owning one of these beauties.
2013 Berkshire 390BH