A block wall is built from units bedded in mortar. The units vary, the mortar varies, and the wall is levelled by the mason's eye over a 3 m straightedge. The result is usually within tolerance, but the tolerance is measured in millimetres over metres, and the finish has to absorb it: a thick plaster coat, or a levelling screed on the wall, or battens.
A stud wall is set out from the floor and the structure, with the studs plumbed individually and the boards fixed to a controlled plane. Flatness comes from the frame rather than from the finish, so it is consistent across the wall and from one wall to the next. There is no mortar to shrink and no unit-to-unit variation.
The difference becomes visible with large-format materials. A 1200 × 2400 mm porcelain slab cannot be pulled flat by adhesive; it needs a substrate that is already flat, usually within 2 mm over 2 m. On blockwork that means a levelling system; on a framed wall it is a property of the frame.
This is why the fair way to compare partition cost is across disciplines. A block wall's price includes the wall; it does not include the levelling, the chasing, the wet trades, the drying time or the loss of lettable area from a thicker wall. The comparison that matters is the finished wall on the day the building opens.