Froggy,
The important distinction in Cat A is that there can be many Cat A procedures for a model helicopter, each allowing a tradeoff between gross weight (payload), and landing distance and/or altitude/temperature.
They are in three general types:
Airfield Cat A , with land back distances and takeoff distances in the 1000 to 1500 feet range. These generally require you to accelerate to a speed where the climb is good even at MGW, usually close to Vy. This is usually at 100% of MGW, because most large helos must meet some Cat A procedure.
Reduced Field Length Cat A, where you climb vertically or even backwards, and then land obliquely into an area that might be about 300 to 500 feet long. This is usually about 85 to 90% of MGW (or so).
Cat A Vertical, where you take off vertically and land the same way. These have two sub-types, those that allow a dip below the heliport height (elevated helideck) and those that do not (ground level). The dip procedure can allow 90% of MGW, the ground level is perhaps 80% or so.
Note that a 10% loss of MGW is perhaps a 30% loss of passengers, since all the rest of the weight items are relatively fixed in place.
To clear up something you said:
"Most companies are pretending flying CAT A, they don't, just imagine they have to reduce the passengers/pay-load by 15% to 45% !!!!!!! no way $$$$$$$$"
In fact, virtually all operators are strictly legal, nobody routinely breaks the rules. Full takeoff-to-landing Cat A is not yet legally required of any operator offshore (but JAR Ops 3 is coming), and is only required onshore in some countries (UK, for one) in conjested city areas. For offshore passenger carrying, enroute Cat A capability is required, and a few seconds of exposure to engine failure on takeoff and landing is allowed and even planned, with proper flotation, exposure suits and Cat B procedures.