Why?

OK so I was looking at some things online that I need. Nothing fancy just some bras and underwear. Why are they so expensive. I can't wear my nice things to work so obviously I need to get everyday things. Bras range in my size from about $17 to $70! Underwear is weird, the regular size is $9 a pair and my size is $10.50! So for the sake of one size I have to pay a extra $1.50 a pair! Nothing fancy just plain high cut cotton panties. So that means that I have to work a whole day (12 hours) to get two bras and two pairs of panties! OK maybe 4 pairs of panties but you know what I mean. But the older ones I have are stained up torn up or as in the case of my bras the wires are popping out :(