Yesterday I tried to help a native Chinese speaker use these words better: in Chinese, there is one common word which means both hope and wish, so she has trouble picking which one to use.

She originally said, while shopping, something like `I hope these items are on sale.` I explained that she could say `I wish these items were on sale`, `I was hoping...`, or `I had hoped...` But I couldn't really figure out the logic of why we use hope in the latter 2 cases but wish in the first case. Is there any logic here or should I just explain that it's an idiomatic thing she has to learn?

I don't need help with the alternate meanings of these words: those are easier to teach.