Used GS market - what am I missing?

Hi guys, I'd like to run something by y'all that doesn't quite make sense to me.

I'm looking to get a large ADV, and going through the options I find that the market is flooded with used GS bikes (1200, 1250 especially) but their prices seem unrealistic to say the least. The posts also state the ad had been up for 6-8-10 months and the things are still unsold.

All the other brands and models act according to market, even the Multistradas... What is it that I'm not seeing about the GSs that keep them at those prices, even though they don't sell?

Thanks!!