I saw this over at GameSpot included with their reporting on a story in the Seattle Times about Halo 2 preorders:
Finally, the final paragraphs of the piece note that downloadable titles for the upcoming Xbox Live Arcade service will cost between "$10 and $20 each." At first glance, this struck GameSpot editors as a rather high price to pay for classic arcade game downloads like Dig Dug. Was this information "speculative" as well? No, said a Microsoft rep. "We have announced an introductory pricing range from $9.99 for basic games to $19.99 for more fully featured titles."
That doesn't sound all that great to me. I was hoping more like $5 for classic games.

Still no word on when it's coming out.