What cable companies make the best cables and sell them directly?

Zavfino for sure. Multiple tiers at various price points. Pick your “poison”. Top performance for each price point.

I also have:

Audience AU24sx RCA cables. My best cable purchase. Runs from Dac to amp.

Black Cat Silverstar 75 Mk1 from my clock.

Blue Jeans I2S cable and ethernet cable.

Jena Labs

For me cables do make an audible difference, but I am a big believer in "Bang for the buck" cables.....nothing I have is more than $300 per cable in my $12,000 system, below are cables I have used with great success and some new ones I'm going to be testing:

Morrow Audio MA4 XLR cables, and DIG4 digital co-ax....Mike Morrow indicated to me that the Level 4 class cables are the best bang for the buck in his line up, and I am incredibly satisfied. These cables MUST be broken in, I used the 20 day (480 hour) break in service they offer.. Right now they have an anniversary sale they've had for several months, Level 4 cables are 50% off of list price....also have a generous trade up program

Anti-Cables speaker cables, Level 2.1 and level 3.1 - Have had these for years, and have never felt they were a limiting factor in my systems.....NOTE: These MUST be broken in, 100 to 200 hours. The 3.1 speaker cables will probably remain in my new reference system....have tried their interconnects, but did not like them....especially compared to the Morrow cables. Have a generous return and trade up program

Cullen Cables C7 power cable (Bluesound Node), and Crossover Speaker cables - I am fond of cable and tube rolling, and will be comparing these cables over time with the GR Research for my second system

GR Research - Will be building a 5 foot pair of Danny's DIY 24 strand speaker cables, great reviews 

Pangea power cables - Use AC-9SE MkII for amplifier and pre-amp, and AC-14SE MkII cables for low current applications. Also have a dedicated 20 AMP circuit for amplifier.....dedicated circuit made more of a difference than any power cable I compared

Supra Cables USB and Ethernet cables - Currently evaluating and comparing to Wireworld cables

Wireworld USB Starlight 8 cable, and Chroma 8 Twinax Ethernet cable, again will be comparing with Supra Cables

Audioquest Vodka 48 HDMI cable for I2S 

Add one more for Anti Cables.  I have a very rough setup in that I need 48' cables to my speaker when I moved into my current house..  They were an improvement to my old, more expensive, 10' cables even though they were that long.

I spoke to the owner about their design, and what he said actually made scientific sense.  I don't want to get into the details because he spent a lot of money getting expert help to improve his cables.

There are probably better ones out there, but not at this price.  And there are many, many more that are worse and much worse.