A partition option should be costed across five lines: the wall itself, the services (chasing versus cavity), the finish (plaster and paint versus a module with a finished face), the time (dry versus curing), and the area (thickness lost to the wall). Most comparisons only count the first line, and that is where the conclusion usually goes wrong.
Area is the line most often forgotten. On a 1000 m² floor plate, changing from a 200 mm wet wall to a 122 mm dry wall releases about 40 mm per wall run. Across a typical corridor and room layout that can be tens of square metres of lettable area — worth far more per year in rent than the wall cost difference.
Time is the second. A dry wall is ready for the next trade the same day; a wet wall needs curing before the finish. On a programme where the floor is handed over in phases, that difference can remove a whole waiting period per floor, which is where the real saving sits.
The advice is to build a five-line comparison for the actual project, with the actual wall runs, rather than accepting a per-square-metre figure. Ask each supplier to price the same scope: finished wall, with services and with the penetrations sealed. The number that comes back will be different from the one in the catalogue, and it will be the one that decides the project.