These are great prices for these two games.
Subnautica: Below Zero will come out of Early Access in early 2021 - there is a good chance that the price will increase then so this is a good chance to grab it cheap. If you liked Subnautica, I think this would be worthwhile giving a try.
Ark: Survival Evolved has been given away for free previously by the Epic Store but getting the Explorers Edition is the cheapest way to get the three DLCs (Scorched Earth, Aberration, and Extinction) adding hundreds of hours of gameplay to the base game. Since the voucher does not work with the Season Pass this is the cheapest way to get the three DLCs.
Of course, if you missed the freebie it will also give you the base game.
Remember: The coupon renews itself after each qualifying purchase so you need not restrict yourself to just one game.
First mention of the coupon: credit to pacificstorm.
Original deal: $15 off Coupon (Min $22.99 Spend) @ Epic Games