^ahh - looking at some reviews and failure images i see you're right, and 350-400W draw is possible at higher clock settings (thats stupidly dangerous even if you had a 14awg PCIe)
a lot of failed neptunes seem to be burning out the PCIe ports rather than the cords though, because all it takes is an imperfect connection to jump a spark or move the load to a different wire/pin and fail the unit.
my advice would be to use my 16awg wire and try to operate the neptune at a setting thats <350W draw. The cable should be fine, but might get warm enough that you want to consider adding a bit of airflow around the wires. As i mentioned before ive been able to do 320W+/cable myself, but any design that demands >250W/PCIe (im looking at you too, sp20) should really just be building extra sockets into the equipment. $2 to add another PCIe socket seems worth preventing several hundred in damage
More like .2$ for the socket, and it's probably even close to 0.05$ in the bulk quantities they are using.
Standard rating for the crimp pins is 9A, so we should be safe up to 324 watt (3x9x12), and it already include some safety margin from the manufacturer.
If you read the datasheet, it gives a numer of mating cycles.
After this number, the material of the pins won't give a contact between pins as good as when it was new, and even in this case, you will be able to draw 9amps per pins with some safety margin left.
But as you said, any imperfect connection will ruin the connector, so using the cables around 250/270 watt is a better idea than to max them out at 300-350 watt.
