Cheapest priced copy (Double Masters 2022): $0.49 at Card Kingdom, near mint, their price list as of .
Elsha of the Infinite 
Legendary Creature — Djinn Monk · 3/3 · Rare · The List · #2X2-208
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
You may look at the top card of your library any time.
You may cast noncreature spells from the top of your library. If you cast a spell this way, you may cast it as though it had flash.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
4 printings · $0.49 to $1.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Double Masters 2022 | 208 | Rare | $0.49 | $1.49 |
| Double Masters 2022 | 492 | Rare | — | — |
| Commander 2019 | 40 | Mythic | — | $0.99 |
| The List | 2X2-208 | Rare | $0.59 | — |
3 rulings from Wizards of the Coast
- 23 August 2019You'll still pay all costs for a spell you cast from your library, including additional costs. You may also pay alternative costs.
- 23 August 2019Elsha lets you look at the top card of your library whenever you want (with one restriction—see below), even if you don't have priority. This action doesn't use the stack. Knowing what that card is becomes part of the information you have access to, just like you can look at the cards in your hand.
- 23 August 2019If the top card of your library changes while you're casting a spell, playing a land, or activating an ability, you can't look at the new top card until you finish doing so. This means that if you cast the top card of your library, you can't look at the next one until you're done paying for that spell.