Sotheby's stunned the art world Wednesday when it sold a single Alberto Giacometti sculpture for $104.3 million in London. That's more than the auction house got last year for its four priciest artworks combined.

Midway through a major round of art auctions in London, the art world is hailing a handful of unexpectedly high prices that suggest a revival in the recession-battered art market. Collectors who pulled back a year ago are back, dealers say, though most are seeking safe bets in established masterworks.