If you search on Amazon for an external hard drive, among those listed will be the Seagate model shown below, a 2TB drive for $80. That would be a great price, except for one missing detail.
Notice in this presentation of the product, it’s shown with a portable computer and no power cord is being used for either device. That’s actually quite common for smaller external portable hard drives. In fact, a power cord is very undesirable since portable use is often in places where there’s not an available power outlet. The product photos provided on Amazon for this drive show every conceivable angle, except the view that would show you the USB and power cord jacks.
In reality, this Seagate hard drive requires a power cord to operate. So, in this regard, the presentation below is misleading or false advertising (by implication). This explains the lower price. The only indication that the drive requires power is a short comment in the features stating, “Power supply and USB 3.0 cable included.” It doesn’t even indicate that it’s a required power supply.
Truly portable external drives that operate on USB power only will be more expensive. For example, Western Digital has a 2TB drive for $114 on sale that is truly portable.