The Panasonic example is good old supply-and-demand in action: more people want the player than stocks currently exist. See also anything from Anya Hindmarch bags to limited-edition cars.
The US numbers reflect the changeover from heavily discounted end-of-line players from Pana, Samsung etc being sold off to fuel the format war to the next-gen Profile 1.1 players arriving on the market. It also reflects people feeling confident investing in pricier players like the Pioneer and Sharp, as compared to just the PS3, which pre the end of the format war was (and still is) the most sold BD player.
Really, I don't think there's a story here. You can now get absolutely storming performance from a £350 player like the Panasonic (which will soon fall back to £299 or even less once production is fully ramped up, which Pana were hardly going to do pre-Toshiba announcment), and even the £200 Samsung is a great buy, whereas six months ago you were looking at £425 for a PS3 and £1000 for the Pioneer.