Really no right or wrong answer here. I drove nearly 800 miles to pick up a used 2004 Hallmark Ute XL. It is a question more of what it is worth to you. To make an actual comparison you would have to match up depreciation against two equally aged campers. As you know the Hallmark usually starts life with a much higher price point than the 850SC. The Hallmark we have seems indestructible with everything still working and the roof solid after 14 years.
I think they are both very good brands and spent a lot of time looking at Northstars, but to answer your question directly, yes, used Hallmarks do do not come cheaply and I think you will find some on the Internet that are older than the one you are researching, but priced as highly.
And an asking price is seldom a selling price (just a thought).
My two cents
Steve and Andra
2012 F350 6.2 gasser SRW LB
Fab Fours front and rear in case we run into a rhino
2019 Northstar Laredo SC