Drives that consume less, go faster and with less weight were perhaps problematic in relationship with storage capacity versus their counterpart in mechanical technology. Consumption is a problem due to the limitations of buses like USB. Some manufacturers tried with cables with two male USB heads although in HUBs or workstations with scarce power supplies or overload might experience issues. For mobile devices, these SSD drives are more suitable in multiple aspects.
Of course today 4TB units aren't particularly for everybody in terms of price but being seen SD cards with 512GB, we are afraid this particular capacity could go much higher with all the available space in a SSD drive.
At least today —trying to invest right— to look for a unit with relatively low capacity it's a very nice suggestion especially to install the operating system and high demanding applications. Time will come and the market, sometimes very inconsistent with prices, is going to equilibrate them after a bit of time.