I swapped over to HD from Dish Network and it added 5 bucks a month to my bill with an initial 50 for equipment. After seeing the quality now I'm looking at a Blueray player or a PS3 with BR. The most expensive part is the initial outlay of cables and upgrading equipment to take advantage of the technology.
rear projector: 0.13 watt per square inch
LCD: 0.28 watt per square inch
Plasma: 0.33 watt per square inch
http://reviews.cnet.com/4520-6475_7-6400401-2.html