upgrade policy different for earring stones vs. E-ring stones!! Why?

[Maxine]

I was disappointed yesterday....the place where I purchased my earrings has an upgrade policy for diamonds...I called re: upgrading my earrings...Each one is about .5 carat...they are not BADly cut, but I thought I would go in and get a little bit bigger, but primarily a better cut...plus I noticed and inclusion w/the IS that I never saw before.......Anyway, the policy for loose stone is something like you have to spend 30% more for the new one.....but for earrings , you have to purchase something double in price.....Why is that? What if I had a .5 stone for my E-ring, would they upgrade it then? That doesn''t make sense!!!! Has anyone ever heard of this?