Robin, you're right. The PS3 was a good price for a Blu-Ray player... Actually, not the cheapest out there (some were as low as $300 on sale at the time of the PS3's release - trust me, I was looking for them) but it was the only actual good one you could get for that price. The thing is, Blu Ray movies were hardly prevalent at the time and far from the standard. Heck, there was still a lot of people thinking that HDVD would become the next standard and Blu Ray would go down the tube - so it may well have ended up being a totally useless addition to the PS3. Turns out it didn't, but again, that's why it's a similar gamble to the Kinect and the XBOX One.
The circumstances are different, true. Another important difference though is, there is not a single game that the PS3 could not have run using a DVD player instead of a Blu-Ray player, whereas at least with the Kinect, it actually has direct gaming applications. Heck, the PS3's Blu-ray drive's slow load speeds actually contributed to it requiring mandatory installs for some games early in the life cycle of the console. If you're interested in a console for gaming though, the Kinect might actually give you access to more games and more features in games. On the other hand, with the PS3 and Blu Ray, it was pretty much Sony saying "Ok, we want Blu Ray to succeed and we need some way to Trojan horse it into living rooms, so we'll unnecessarily force it onto people interested in Playstation and have them foot the bill for getting it to take off." It was a gamble, it was almost entirely at the customer's expense, it worked, and now we all pat Sony on the back and say "What a great idea!" even if we were in an uproar when it first came out. Five years from now we may be sitting there controlling our TVs with our index fingers saying "darn, I wish the PS4 had this in it" like many of us do with the XBOX 360 and Blu-Ray now.
Don't get me wrong, the extra $100 sucks for people who have *no interest* in it, but frankly, I haven't even upgraded my DVD collection yet, nor do I ever intend to.. And I still paid the Blu-ray fee in the PS3. Tough beans, I guess?