That is how growth works.
first 2+growth_factor classes are cheap then the rest is expensive.
for a 1 growth character it would be 100,150,200,1000
for 2 100,150,200,300,1000
soft exp [100,150,200,300,400,500,650,800,950]
hard exp [1000,1500,2000,3000,4000,5000]