I think it's one of those two sided deals. I've been looking for a 75D for a good while, most of the market offerings seem to have fairly low miles. While most of us agree miles aren't a true indication as they are on an ICE car, when presented with less than more, all else being equal, the lower mile versions are selling first. Thereby driving the cost on higher miles down when sellers have to weigh the cost of keeping long term for hopes of a buyer vs selling sooner at a lower price.
Just my $0.02