I'm with Isle Of Man on this one: either buy something completely disposable or something expensive with proven quality. Like him, I try to buy into the expensive stuff at the lowest price point I can find. I travel quite a bit these days, so having bags with good warranty is a must (plus I have to valet check my bag on a leg most of the time).
I got both my current bags this way: a discontinued 20in B&R which I got on sale for $150 and the Eagle Creek Tarmac 20x in I use weekly and I got for $120. While sometimes I'm tempted to buy more bags (like a tote, a backpack and a Kirkland to use as checked luggage), with my current bags and travel pattern I don't really need them, since I have a good replacement bag in case the other one needs to be in the shop which hasn't happened yet, but I am sure it will.
Try not to buy a bag on a rush. If you're patient and don't need a bag for "next week's trip", you can find great deals on high quality stuff.