It's definitely cheaper to buy it packed in with the system. Of course, future price drops will depend on how well it is selling. The Jury is kind of out on how well this product will sell. I can tell you that myself being a gamer, I am cynical of the product, but it really is not being targeted for my demographic.
But a large marketing budget always helps to sell a product and since Microsoft is expected to be spending in the area of $ 500 Million dollars marketing Kinect I'm pretty sure they'll move a lot of units this holiday season. (Source:
http://www.computerandvideogames.com/article.php?id=270209)
Usually things like this don't see a price drop until at least a year after it's release and if it still selling well 2.
If this is a gift that your child "HAS" to have this holiday season, your best bet would be to get the 4 gb model xbox 360 with Kinect packed in (
http://www.bestbuy.com/site/Microso...nect/1162439.p?id=1218228657992&skuId=1162439). This comes with "Kinect Adventures", a pack in game similar in scope to Wii Sports. This package retails for $299.
Separately, xbox 360 4gb model is 199.99 and Kinect w/ game pack in is $149.99.
http://www.bestbuy.com/site/Microso...18212157998&skuId=1036858&st=kinext&cp=1&lp=5
http://www.bestbuy.com/site/Microso...sole/1162184.p?id=1218228678498&skuId=1162184
Something to keep in mind however, if your child is or will be interested in Online Multiplayer gaming, they must have a system w/ a hard drive (the 4gb model only has an internal flash drive, not a hard drive). Now you can get the $399 250 GB system w/ Kinect pack in, or you can opt for the 4 gb version for now, and if/when your child becomes interested in playing online (or when you decide you will allow them/they are old enough) you can purchase an Xbox 360 certified hard drive.
Sorry it's so complicated... What happened to the days when you could just go out and buy a Nintendo and it would play all the games, eh?
*Edit* Heh, I compose a novel and Kalliyan1 manages to spell out most of what I said in 7 concise short lines.