pokemon cards back Card Backside in High Resolution by AtomicmonkeyTCG on DeviantArt A Look At The Back

Two life for one card is pretty much the norm (with Card not found you are only up one card), but usually the rate is somewhat better, because theres some other benefit involved (like the scry 2)

Mox Pearl (Alpha Edition) $34,800 PSA 10 Gem Mint Why It's Valuable: The key to fast white mana acceleration

The effects are all good for you or bad for your opponents, although in some cases you may not be able to take advantage

Prevent that Villainous Wealth or Torment of Hailfire of reaching X = 15, dont allow the voltron player to keep their Rogues Passage and get rid of that Urzas Saga before it can tutor up an artifact

So, essentially, extra turn spells have a rate (in the modern era) of costing a variable five mana, a la Time Warp