I own a website selling custom made dresses

now i want to set changeable price according to the quantity bought.

For example

Qty Price

1 100
2-5 90
6-10 80
... ...


How should i do to realize such an idea?

I need to set this in batch,not set it one good by one good

If you guys who understand my question and know how to deal it,pls help me,thanks so much!