The Real Deal‘s Data Book 2008 tumbled from our mailbox last night. Among the myriad of factoids was this one: The average sales price of an East Side Manhattan townhouse increased 317 percent from 1997 through 2007 to over $10.63 million. The average sales price for a West Side townhouse increased 227 percent to $4.61 million. And, 10 years ago, your average downtown townhouse would’ve cost $1.2 million, give or take. Now? Nearly $6 million.