Okay well first off, eBay can be a great tool, and it can be a great big TOOL. If you look at the pictures on those auctions you will see either a really tiny box with two terminals or you will see a simple resister jumping two pins of the MAFS sensor. So at that point you are paying 10$ for about 1$ part. Secondly I am a found believer of "You get what you pay for" and "You'll get your money's worth." Pay 10$ and get about 10 days of use. Pay 1000$ and get about 1000 days use. Thats just what I have learned with un-branded parts. But hey if you get it let me know how it works.
~GKauten