Good point. Let's say it's 30$ for Blu-ray (I had estimated that earlier anyway), all things considered, beyond the cost of a DVD drive. That's probably a little on the high side now but whatever.Don't forget the added cost of the licenses to allow BluRay movie playback. This is a fixed cost added to every PS3 sold that Sony is powerless to cost reduce. I have no idea how significant they are, but you can't just ignore them.
In the case of the 360 this cost is rolled into the price of the add-on.
For that you get a drive tech that needs lower rpms for the same transfer rate so it's either faster at the same rpms or quieter at the same transfer rates, or some combination of the two. Plus you obviously get more storage and a built-in Trojan horse for the movie division. Yes, it is a bump in per-unit costs that is large enough to still be felt, but I do think that it's money well spent, both from Sony's perspective and from the consumer perspective.
I just want to have that "OMG BR is 200$ and one yier delay lolz" stuff off the street. The exact amount isn't so important, but we should at least be getting the order of magnitude right.