To original poster of the thread,
here is how I do it: 

compare prices everywhere online.
I've a prime account with Amazon.com and that's where I compare my price. It's one of the best and the largest online retailer in the world today.
Now, ebay is not what it used to be. To much corporate chains are on ebay now-a-days and it's literally another online store rather than auction site. They do have auction feature but it's gradually diminishing out of the view.

So, say, if I've to buy a laptop, first I'd search it on ebay. After I found it, I'll give another search on amazon.com. Then on techbargains.com and tigerdirect.com. Now, I compare all the prices. Then I get the phone number of my local electronic stores off google, call them and ask if it's available, if it's ask how much. Don't even have to go to the store. If they've stuff then I make a trip to store and check all the features. If I like it, I come back home and buy it online. If I don't like it, I look around. Few of the products on ebay, I found it quite pricy than other online stores, blame it on corp chains listing their products out there. But if you know how to dig ebay up, you will always save money out there.

And, always use paypal as payment option as it's the most secure way to do business. If someone asks for wire transfer, then be ready to lose your money or be ready to be the victim of online fraud.