You do still have to pay the mana to cast the Vehicle or artifact creature you exile, but since there's no mana needed to be used for Sanwell's effect in the first place, you should have access to however much mana you need
Jump right into the battle
Secondarily, you could think about Sejiri Steppe, Sandstone Bridge, Windbrisk Heights and Idyllic Grange
More goodies came with Modern Horizons , where Snow was a major theme of the Blue/Green color combo (Abominable Treefolk), but stretched into other colors, too (On Thin Ice, Dead of Winter)
It is almost an exact reprint of the Black and White Plasma Snorlax that saw a lot of play in its time to block opponents from switching and lead to many unpleasant deck-out situations
Yes, so Prosper, Tome-Bound sees that you exiled and cast a discovered card and would create a treasure