matthiask/plata — comment on commit 6fb85c6dd44d7cf6dbdd33cfbca083479b0d3c4b
File:  line 0
By matthiask:

That's not optimal. There is no way to differentiate the price by quantity in cart if it's done this way, because there's no way of knowing how many items are already in the cart at this time.

(Btw, does this even work at all? Order.modify_item fetches the price again, and without the additional fields.)