Console hardware costs can be best valued when taken into the consideration of product refresh cycle. It's like buying a macbook. They offer an upgrade every 5-8 months, so it would make much more sense to purchase at the beginning of a refresh cycle. For PS3 vs Xbox, it's the same thing. Their relative prices are set by professional analytics to their worth. The best way to decide which to purchase in my opinion is to actually look at their individual refresh cycle. I would argue that they are both fairly priced. They are overpriced at the end the cycle and underpriced at the beginning of the cycle.
hope it helps