The cost for your new TV toy will vary greatly between sizes and manufacturers. But for anything over 35 inches in plasma or LCD, expect to pay about $1,200 to $2,000 for a decent model. Over 60 inches and the prices go up rather dramatically.
It's often best to stick with a recognizable brand, and comparison shopping for price alone is much easier these days thanks to the Internet. Even so, I'd still suggest at least checking them out in person somewhere before buying online.