And I've bought the domestic tickets at Priceline.com

I've been asking around and heard it's the cheapest website to buy flight tickets.

I was supported to buy tickets "SFO -> Chicago", "Chicago -> NYC", "NYC -> SFO". But after I searched them on Priceline, I found that buying round trip tickets is cheaper because I could buy it as a "Name your own price" way on Priceline. So I've bought it as "SFO <-> NYC", "NYC <-> Chicago".

And now I'm ready to fly! :)