If you're looking to find an XBOX 360 for the lowest price on eBay you need to try some common misspellings.  I was able to find an xbox 360 (core) system for $247 with the search below.  Keep trying every day; the key is to find one right when it is listed before the spelling has been corrected.

XBOX MISSPELLED SEARCH

Misspelled words are a GREAT way to find deals on EVERYTHING on ebay.  Another way to find great deals on products like the XBOX 360 is a cheapjerks.com membership, but that costs money.

Good luck and I hope this helps you find a great deal on an XBOX 360 like I did (more than once)!