I'm backing away from the question a bit... You aren't buying a price, you are buying a motorcycle. I focused in on drilling down to what motorcycle I wanted to buy, then went out and found the right deal for me.
The F800GS is a seductive mirage... But getting one will not be easy, as the sign up sheets have been in the dealerships for 6 months and in most cases already have enough buyers in waiting for that dealerships first year of bikes.
I have an 06 DL1000. I had the BMW F650GS prior, and it was an excellent machine.
It was enough bike to give me the Alaska itch, but not enough bike to take me there *IMHO.
I knew what I wanted to do, and had an idea of what size I'd need, and like you - other BMW riders turned me on to the Strom.
Rode it and fell in love. Now farkling like no tomorrow.
The riding you envision sounds better suited for the DL650, or F650GS/F800GS.
I'd suggest one of those 3 bikes to get back into the saddle.
Like you, I hadn't ridden a street bike for 20 years, so it was a new thing.
On my BMW, I owned it for about 8 months, put 4,000 miles on it, and sold it for just a few hundred $$ less than I had invested.
I buy used, motorcycles are an item that a lot of people think they want, buy them new, and within a year are kind of tired of the thought or in need of cash, and sell them with the thing barely broken in. There is a small element of risk, but in my opinion not much.
Now is a great time to be thinking "buy", because private owners and dealers alike are prepping for winter and thinking "sell".
2006 DL 1000 - Graphite
Current Odo - 7200 miles
Pointless Profanity Club - Member #2