At their core, Ramp decks generate a tremendous, mostly permanent, mana advantage which they leverage to kill the opponent
If you need a board wipe, Nuclear Fallout should have you covered
Where prices really spike is when cards appeal to both groups, with a card like Sheoldred, The Apocalypse a prime example being a major player in multiple competitive formats, and a favourite in Commander
Chart shows the price of Mawile V #TG17 at the end of each month going back as long as we have tracked the item.
(10/15/2006) Evermind has no mana cost, which means it can't normally be cast as a spell
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions (such as that of Grounded for Life's first ability)