Suppose you want an acidic solution to carry out a chemical reaction with 2 moles of NaOH. Which sample of acid is the best choice for you?
(Atomic weight : S=32,Cl=35.5 )
 

The reaction is having follows, 

$2\mathrm{NaOH}+{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{Na}}_2{\mathrm{SO}}_4+2{\mathrm{H}}_2\mathrm{O}$

2 moles of $\mathrm{NaOH}$ requires 1 mole of ${\mathrm{H}}_2{\mathrm{SO}}_4$.

Since $\mathrm{HCl}$ is mono basic, two moles of $\mathrm{HCl}$ would be required which would exceed the cost of 50 .