I dont get it

I try to keep my prices as reasonable as possible, but some people just dont get it. For example with shinys, i always state 1:1 + 500c / 2:1 and i get 1 common plus 500c instead of a shiny and then they try to go up to like 1200c, which im not in need of. Its so annoying to make such good prices and still be lowballed like crazy