Just saw this yesterday. It looks as though they took the cover off the stock 15" wheel and then chromed the wheel. I think it looks pretty sharp.
Dealerships will often do this. I've seen the same thing done with the 2nd gen 15" wheel. Friend of mine also drives around in a 2nd gen Prius with a chromed, 6-spoke Corolla wheel. He said the car came like that.
There's something funky about the link to the image. Click on it to get an enlarged image and you'll get the proper aspect ratio. The decal seems genuine. I don't know how they got it, being that the allotment ran out before the 2010 hit the market. Or so I thought.
From what I remember. If you are replacing a car that was totaled and had the stickers then for the new car you can get replacement stickers.
An eBay seller offers chromed OEM wheels. I'm going by memory (dangerous), but I think they're about $1000 outright; they are $525 if you give them your stock wheels in return. Here's one of the auctions -- for chrome wheels on an exchange basis. They also have Gen II wheels in chrome. TOYOTA PRIUS 15" CHROME WHEEL EXCHANGE GENUINE NEW 2010: eBay Motors (item 200481377416 end time Jul-08-10 16:04:21 PDT)
Interesting. If the rims can be chromed out, is it possible to get those 15" rims powder coated (black/gun metal)? Would that be a cheaper option? I like the look of the rims on the 15" wheels rather than the 17" wheel, but not chromed. Just curious.