the issue driving these prices is the gmt900 makes a gmt800 feel like an s-class mercedes in terms of interior fit and finish and build quality. and the 15-20 suburban/yukon is substantially the same powertrain/suspension/ driving experience as a 900 but with a better but tighter space/feel interior and the 900 wasn't a significant improvement in ride quality over an 800. and the middle row seats/legroom and rear cargo area got progressively smaller through those next 2 iterations until the 2021 redesign.
so there's nothing truly worth spending money on until you're over $45k in the used market, and so $6k for a clean half ton gmt800 seems to be a relative bargain in the marketplace.
it's jaw dropping to me that they could window sticker this gmt900 escalade as their flagship offering starting around $80k with halfassed fake woodgrain decals on the trim bezels and a pep boys wood-look steering wheel cover doppleganger wheel then call it good and then go to the market knocking on 6 figures when heavily optioned while retaining a straight face.
2010 (GMT900 ) escalade: