The floor is a 4-mana deal 5, and that's very playable -- but this will often cost two and give you some sacrifice synergy
(A desire not helped by my sons mad luck at pulling the Obsidian Flames version from a pack.) My guess would be the Japanese version will start selling for around $300 pack fresh, and the international version next year will easily hit $200, before coming down to about half that
For most people, change, even positive change, is difficult to deal with
Scapeshift is traditionally a powerful option against decks with a lot of discard spells, as Scapeshift after turn four or five is often a kill by itself
For example, if the card is a creature card, you can cast that card by paying its mana cost only during your main phase while the stack is empty
Despite being two separate cards, they fit in together