Solid core power cords under 300$ - List of manufacturers ?

DIY was brought up as an option, and romex was also brought up by at least one other...mainly, because romex IS an option. And definitely solid-core. 

As far as that goes, options would also be buying AC wire (same as in romex, just not in the extra bundling sheath), or, even stranded. Seems bulk was also brought up/used in this thread as well. 

To the point, buying bulk isn't just cheap, but one could easily make the same cable in stranded or solid and see if they hear a difference. 

One might experiment with different plugs as well.

Romex is not designed, manufactured, or Listed, to be used as a power cord. It is designed and Listed for use as mains power wiring fastened/supported rigidly in place. Romex, NM, cable can only be used in places/locations as approved by the NEC, (National Electrical Code).
.

I`ve used solid core powercords for about 25 years. DIY, 12awg shielded. 9awg to poweramp. (big guy)

They do not "do" anything, but they are the only PC without any loss, distortion aso

Btw; speakercables should be made the same way, but needs to be of bigger area because of the lower current on secondary side

jea48; Romex will outperform any manufactured PC