Excessive late fee charges

I had 2 individual instalments that were due to off on 1 April,I unfortunately missed the deadline and incurred late processing fees. From a total of R2066.43 I ended up paying R2877.38. Isn't an additional 810.92 a bit too excessive for a week's late payment payment, this equates to 40% extra in a week and 160% for a month's worth of late payment. Doesnt make sense