I had a surge guard for my old 30a 5er. When I bought my Bighorn 3400RE I went and purchased one of these.
Surge Guard @ Tweetys. It runs $343.41. Beats the $500.
I have only one complaint about the 34750. The part that plugs in to the shore power is really a little short. I find that at some campgrounds I almost have to tie it to the post so it will not fall out. I also bought the lock. However I figure that if someone wanted the Surge Guard they could take the entire shore power cable or cut it off the main cable.. then I am really out more cash.
I probably spend a bit more on preventative than most. But so far it has paid off for me. Hope this helps.