Apple has bought companies in the hundreds of millions of dollar range several times (generally suppliers or tech vendors; treating "better online services" as a form of technology like a fabless semi or fingerprint sensor seems reasonable.)
Due to the price premium for being a "winner", buying a $100-200mm (in a down market) really well executed SAAS company for $1b (now) isn't that big a deal when you're sitting on hundreds of billions and tens of billions a quarter in profit. Online services will ultimately be that important to Apple's success.
Not in the billion range, but they were acquired by NeXT for negative $404m (in 1997), they acquired PA Semi for $278m, Quattro Wireless for $275m, C3 Tech for $267m, Anobit for $390m and AuthenTec for $356m. They are clearly willing to pay hundreds of millions if they think it's worth the price.
