This page shows current market prices, recent eBay sales, PSA graded values, and price history for this Common card from Roaring Skies
When you consider that buying a booster box worth of packs from Walmart or Target will cost $280 and that a sealed box with the Ultimate Box Topper is about the same price, assuming you have the upfront money to buy a box, it's the best way to go
However, in casual games, players can always rule zero these types of cards
Overall the decks are great
If you open one of those Rares, you then have a "free pick" for whatever will improve your deck the most - an Uncommon, or that Rare/Mythic (which is now worth 20/40 gems to you)
Meanwhile, mythic Mystical Archives are a bit worse