It's much cheaper compared to other Pre-U courses.
From rough calculation you can settle whole Form 6 within RM 1k, whereas you've to spend maybe up to 10k or more for other courses.

Anyway, STPM is said to be much difficult compared to A Levels, SAM, SAT etc. More effort is needed in order to score well, and depends on your luck, whether you get a dedicated teacher or not.

STPM cert however, is kinda limited to the university within this region, going as far as Aus or NZ.