PING distance sensors prices

Hi, I have a short question, I saw on Ebay a lot of distance sensors that look very similar but can cost from 2 to 12 uss, what is the difference??

nahuelv: Hi, I have a short question, I saw on Ebay a lot of distance sensors that look very similar but can cost from 2 to 12 uss, what is the difference??

$10? Is this a trick question?

nahuelv: Hi, I have a short question, I saw on Ebay a lot of distance sensors that look very similar but can cost from 2 to 12 uss, what is the difference??

You should probably give more details. I searched ebay and found the HC-SR04 to be very cheap. I was very surprised. They aren't available yet in my country.