Add-ons To Collections

I think this is a bug, and hadn't noticed it before.

When creating collections, we allow add-on prints. If the same image, a discounted price. That works fine.

But, if they select a new image, there is a higher price for say 1-8x10 of a new image. That works fine as well. But, additional prints of that same new image are supposed to be the discounted price. And, that works fine if it's a different product. 

But, if someone adds two of a product of a new image, the system seems to charge the same higher price for both units of the add-on, instead of the higher price for the first, and the lower price for the second. If a customer adds 1-8x10, and then goes to add 1-5x7, the discount works. But, not if they add 2-8x10s of a new image as the first additional product for that image.

Does that make sense?

I've made a note to look into it.

Thanks.