Update 24/06: Absolutely massive price drop of $0.04. Now brings it to $21.58
The Complete Edition of Horizon Zero Dawn was recently announced to be added to the PS Hits lineup, meaning a juicy permanent price drop.
At $21, this is great value for one of the best PS4 exclusives, as not only does it include the base game, but also the Frozen Wilds DLC which costs $30 to buy separately from the PS Store (it does get discounted once in a while, but even then, it only tends to drop as low as $15). As such, I'd argue there's almost no reason to buy the base game now considering the cheapest at the moment appears to be $17 WITHOUT the DLC.
Don't forget to use cashback to bring this down even further.
PS. It doesn't 'officially' get added to the PS Hits Collection until the 28th, hence why it's listed as a Pre-Order.