This hair is also cyclic in growth pattern and there are about 20-30% growing at any one time.
The growth is less agressive and there are fewer nerves in the area so it is (less)painful to wax etc.
The problem with legs is the surface area they cover (36% of the total body) the chest and abdomen the same and the back is also 36% too (Wallace Rule of Nines is used to formulate the surface area). So whatever you use it will invariably mean a lot of it.