Dawn, I'd say a great price for a MIM strat would be $250. Which is precisely in the range you figured. Again I recommend keeping your eyes on Craigslist. eBay is a bit pricey. There are a lot of buyers out there on eBay that seem to have a compulsion to buy sight unseen guitars at retail street prices. If you are close to a major city then watch Craigslist everyday. When a good deal pops up you have to jump on it fast. And you can hold it in your hands before your buy.
This was just a week ago in Orlando's Craigslist...
http://orlando.craigslist.org/msg/217671327.html