Less than SGD $5 for a Bluetooth Headset?

I just bought this off eBay. Only USD 3.78. I needed a replacement for the one that is threatening to give up on me.

Now the price is so unusual that it is reasonable to

1. Doubt it
2. Reveal my ignorance on the economics of this device.

I  hope it is 2. and I would have scored a nice bargain.

It was so inexpensive that I would rather risk the few dollars than do the research to tell if this is too good to be true. Of course if it weren't listed on eBay, I would assume it is a fraud. At this price even a toy device is more expensive or may be just typically over priced.

Just thinking again. Perhaps it would work but only good for a week, a month?