I can't emphasise this point enough. Don't just check one site for the item you want. First, do a general search on the item. Next, go to the manufacturer's website and find out the recommended retail price (RRP).
Note: make sure the site you are visiting is in the correct region. A few times I've seen a price and thought wow! That's cheap! Only to find out it's a .com site not a .com.au!! Argh!
Also, there are a few sites such as shopferret.com - these sites seek out different online stores and come back with a number of different prices for the same item. Amazon.com has a similar feature. Check out reviews, ratings and any other info that helps you decide if its really what you want.
Research research research!