Diablo Prime Evil Upgrade

I have a question,

I have D3 and Reaper, yet for some reason the collection and the upgrade are priced the same, both at $38.99, this makes no sense to me. If I own part of the bundle, why the upgrade is the same price as the whole. Even at retail price the difference in price is a joke, $2ish dollars less for the upgrade.

I would like to know the reasoning behind this “brilliant” pricing policy too

I would like to know if this is intentional as well. I came for the holiday sale to get the upgrade at a reduced price, but right now there is no reason for current owners of any D3 content to purchase during the sale, which must be a mistake.
As there is no direct incentive to buy this during the limited time, they will miss out on a lot of impulse/future plan buys like mine would have been.