for (e.g. my browser automatically shows me the prices for the same DVD at different online stores on the web) と of (e.g. my browser automatically shows me the prices of the same DVD at different online stores on the web) はどう違いますか？説明が難しい場合は、例文を教えて下さい。

There is no real difference but the technical difference is:

the price of X = the amount of money required that X has assigned to it
the price for X = what you have to pay in order to get or attain X

Let's say you go somewhere where there is an item that the owner was not planning to sell. There is no price on it. You say “How much do you want for it?” The owner says “$20.” There was no “price of” the item but the “price for” the item is $20. Yeah, it’s really, really subtle.