It's the store's responsibility once they've bought them from Hasbro. That's what clearance sales are for, to clear out at a loss, stuff they bought too much of.

And Hasbro do the same thing if they have excess stock that stores aren't initially wanting - we see them cheap at Toyworld or BigW.

The only time toys would be destroyed or discarded, is if they are unsellable at any price, to not even cover the cost of shipping them. And even still, making a loss on one product can help sell another as part of the deal.