Purchasing a used Gateway

Gateway is basically a cell phone so yes, you could swap out the SIM card so it has the same number that is already on your account, but TMobile may not allow you to activate the IMEI of the new router. I would recommend you get a written acknowledge from TMO stating they support buying your own router. There is also the question if the new router would get future firmware updates.

However, like a cell phone, if any of these units on eBay are stolen, I would imagine Tmobile has already blacklisted the IMEI like they do with phones so even if you get confirmation you can bring your own device, you run the risk of it still not getting service if IMEI is blacklisted.

Someone in another post said that if a person kept a gateway instead of returning it, and they paid T-Mobile the penalty (I think they mentioned $370, but don't quote me), then T-Mobile has sold it to them.  That is not true.  If you rent a piece of equipment and forfeit a deposit due to non-return, that does not constitute a sale, nor does it legally transfer title.  Even if someone on eBay says they've paid that penalty, the device still is not legally theirs, and several people have reported on forums that T-Mobile has, in fact, refused to activate such gateways. I'm like you--I'd like to have one on which to experiment attaching an external antenna or just have as a backup, in case my original one dies, so I won't have to wait for a replacement, but at this time, T-Mobile isn't allowing that.

The interesting thing is the seller who has sold 178 of them over the last year with more still to sell. They are being sold as "Open Box". That seller sold some for as much as $250 back in February and is now selling them for $99. Seems like a liquidator, but if that was the case they would have had to have gotten them from T-Mobile. Or, I suppose, somebody could have stolen a truck load of them.

The other explanation is that Nokia gateways are being phased out for the Arcadyan. If someone wants to buy all the returned Nokias and remaining stock then why not? Just message the eBay seller and ask if the guarantee if the the units they are selling are guaranteed to work on Tmobile. As long as you get a "yes", you have it documented on eBay and can return with eBay guarantee.

Thanks Cali Cat for the insight.  Your correct, don't think I'll go down that road. Regards...

The same thing happened when TMobile had their home phone service that used a router with a sim . Once they started phasing out the service ebay was flooded with the routers

I bought a brand new router for pennies on the dollar to have as a back up since they grandfathered the plan.