This is quite true, just forgot to mention it in my post. I have a feeling you still failed, though, because:
First, the 360's drives aren't proprietary - they're are essentially normal drives with the 360 firmware on them, but the 360 seems limited to using certain size drives.
More to the point, PS3 drives are completely normal laptop drives, and readily accepts the 9.5mm variety (and probably slightly bigger).
An official 60GB 360 drive is (I'm guessing Newegg's price is in line with what you found; Amazon is way outta whack) listed at $89 in a kit, and I did find a 160GB kit for the PS3 for $89 as well, on Amazon, which lists the 360 drive at $115 by itself. Is that what you found?
Please tell me you found the 360 drive for a price in line with [http://www.newegg.com/Product/Produc...der=PRICE]this list[/url] and that I'm just reading too much into your comment.
For extra shame, let's all consider that a PS3 can accept standard 3.5" computer drives, which are significantly cheaper for the same or even more storage capacity. All you should need is the appropriate SATA cable.