In my case $120. Audioquest NGR-2 (way back when). Since then, haven’t just drank the KoolAide on PC/power delivery. I chugged the entire pitcher. (I’m the guy who did the "audiophile power cable" survey a few months ago).
I’m sure there are cases where all the stars line up, power delivery falls into place quite nicely (as suggested by @carlsbad2 ), and the factory-provided/hardwired cable will do just fine. I just haven’t heard it yet. But, I’m open-minded.
For me, I have yet to hear a case where a premium PC didn’t make a difference on ANY component at ANY price. As dealer, we’ve put, literally, hundreds of premium PCs in customer’s systems. But, admittedly, my experience is limited to mostly 4 figure electronics. We currently do performance mods in the shop, some involving internal power delivery upgrades. The differences are simply stunning. I keep 2 identical 100x2 NAD power amps on hand. One completely stock. One with performance mods. The upgraded version doesn’t just sound better. It sounds like it was designed and built in a different factory to a much higher standard. Take the top 10 adjectives we like to use to describe "better sonics" and they are all there,, in abundance..
Here’s another case in point. We were missing around on the bench with a little (less than $100 retail) Class D plate amp. We were seeing how this thing might work in a cost-effective, stealthy office system mounted to the modestly panel under a desk. I have to say that, while we reached the stealthy goal, the sound quality was harsh, and down right nasty. Then I thought: "What the heck?", reached for a $69 AQ power cable and swapped it out on the outboard power supply. The sound immediately calmed down, there was some bass presence when none was there before, and the soundstage became somewhat 3-dimensional. The point: Even cheap stuff benefits from premium PCs.