I'm allergic to dust and I live in a fairly dry climate, so my lab accumulates dust at an amazing rate. I decided to
look into the issue, by identifying where the hot-spots are and running a few experiments with humidifiers and logging the
quantity of dust over time.
I came across the GP2Y1014AU0F PM2.5 module and I bought one for about $5. I didn't know anything about it at the time
of the purchase, so I didn't know what to expect.
It says SHARP on the back and I may be wrong about this, but I have strong doubts that the ones you find on eBay are original.
I say that because I noticed that the specs on the eBay page are slightly different than the specifications you find in
the original Sharp datasheet, but that could be due to the seller not knowing his merchandise.