Price of iPad in Amazon

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I am looking to buy an ipad in amazon to use it outside US. I am confused on the price as the same model is listed between 400-800+. Also it has to be factory unlocked. I contacted a seller and he said for that to work outside US, it has to be switched on and used for 20 minutes using a US sim in US soil. I find that amusing as i've used unlocked phones brought from US.