The goliaths. T. blondi, T. stirmi, T. apophysis. The largest tarantulas by mass on earth and among the most demanding regularly kept.
They need genuine humidity, not the vague damp most tropical species tolerate, and they will not molt properly without it. They also carry the most irritating urticating hairs in the hobby by a wide margin, potent enough to cause respiratory reactions in an unventilated room. Anyone recommending these to a beginner because they look impressive is doing harm.
T. blondi is CITES listed, which restricts international movement and pushes most of the market toward stirmi, a slightly smaller animal that is easier to keep and less expensive to buy. That substitution is the main price dynamic here: as stirmi supply improved, blondi became a specialist purchase rather than a default.