I was going to proxy up "The Cube You Can't Afford" ... the 360 most expensive cards to acquire in any tournament-legal form in Magic.
But it turns out it would be rubbish to play with as it's basically just a load of ABU, Arabian Nights and Portal: Three Kingdoms rares.
For interest's sake here's a visual spoiler of the 358 of the 360 approximately most expensive cards in Magic in ascending price order:
(Prices, order and everything else fairly approximate and woolly - appearance of <a class="card">Divinity of Pride</a> will remain unexplained.)