Price stability still depends on factors such as reprint risk, demand, card popularity, grading population, and wider market conditions
These additions help ensure you'll always get instant value out of every Sugar Rush Speedway, Finish Line you find
Separately, both cards are good, with Eldrazi Displacer getting blockers out of the way or blinking our own creatures for value or to save them from removal, and Mangara of Corondor is basically a slower creature version of Oblivion Ring
BPhillipYork: This seems decent for discard decks and over costed otherwise, a solid enough way to get an evasion ability onto a Commander, basically
Beastmaster Ascension decks want to pump naturally small creatures, and both Creeperhulk and Gigantomancer can help make combat math frustrating for opponents in those kinds of decks