Hey, Rando
I got the BRP backrest last spring, and yes, it's very expensive, and silly how you need to get a rack which becomes far less useful with the backrest installed.
At the time, it was pretty much the only game in town, and the lovely bride and I already had a trip planned.
Having said that, it's the most comfortable and secure she's been on any of our bikes since 1986. Now, we've never had a nice big Gold Wing, but have had a variety of other American and Japanese bikes, and she's never felt "held in" like on the Spyder with that backrest.
We don't change it often, but it's nice that it has a little bit of fore and aft adjustability. I like the look of the thing when riding solo, too.
I don't know if the price has increased, but it'd be great if you could pick one up off eBay or somewhere for less than MSRP.