Well to give you an idea why it mathers, as I said they cost $19 / pair in Sweden.
I will be doing a long holiday trip in the caribbean. I will be flying from Sweden to Newark and from Newark to Fort Lauderdale, you never know if some props gets bent on the flights. From Fort Lauderale I will be going on a cruiseship and will be doing 11 stops during 22 days in the caribbean. I need to hand over my drone to the security staff onboard during the days we sail. The only reason I bring my Phantom 2 is that I want to film the caribbean nature. I won't be able to buy ANY spareparts during this trip, this means that I need to bring spareparts with me. I will be needing a lot of props, if I don't want to take the risk to not be able to fly due to broken/bent props. Even if the cruiseline will be responsible if my Phantom gets damage during "their care" that won't help when we are in the caribbean since there's no spareparts availible.. Even if no props are damaged during the transport there's still the risk of having a crash and damaging the props.
The difference of four dollars between Sweden and the U.S isn't that big if you just need one pair but if you need 8 pairs, well then the numbers add up. Add to this that I need to buy at least two batteries, ( they are $129 in the U.S but in Sweden they are $205), new landing gear since I added the gimbal and GoPro, at least two more memory cards ( I want to be able to change cards after a week so that I at least have some fotos/films if I lose the camera). I have the GoPro only for my Phantom, I have a Sony HDR-AS100VR for normal "action cam use" and then I have a normal cam for stills = I need a lot of memory cards. All in all it adds up on the Visa bill..
If you think that I'm cheap well, I'm not made of money
Back to the props, I know well how it works in China when it comes to caraudio and the same factorys builds products for different brands and there's only small cosmetic differences between them but the pricetags are often miles apart depending on what brand you buy. This made me guessing that the same goes for props.