Indian fossorials from the Western Ghats, T. truculentus and T. insignis, and the market here is defined by a border.
India prohibits wildlife export, and has for a long time. Every legal Thrigmopoeus outside India descends from stock that left before that, so the entire global supply runs on a closed founder population bred in Europe. That is the price story and it applies to every Indian tarantula genus including Poecilotheria.
The animals themselves are moderate-sized burrowers, old world in temperament, drab with some subtle patterning, and undemanding beyond substrate depth. Nothing about keeping them explains the price. The paperwork does.