It is PET sleeve (polyester). It is pretty expensive, mostly because retailers here sell it at high prices (small market and no competitors). For example you can buy my graphics card in USA for 799.99 - normal price, and you can apply discount coupons to get a better deal... Here, the biggest online shop in my country sells it at 890€ (1050 USD)!!! I was lucky my friend got me a great deal.. And that goes for everything. This sleeving cost me 2.39USD for a single meter.
So that illustrates my point, I simply could not give you a decent price, because of the cost of the material. But I would recommend going with this site: https://mod-one.com/custom-pc-cable-extensions/
They are professionals, so they will make it look even nicer than I would, and prices aren't all that bad (they are almost the same price as the cost of the material needed in my country). They will make even the whole cabling, not only extentions and they use the same material as I did (even the same brand).
But I do take that as a compliment, thank you :)
Too bad, I will talk to them though. Thank you. Seriously in awe about your build. Thank you for blessing us with it.
No problem. But maybe you could try to do it yourself, I am sure you would love the activity. And if you are worried about spending too much money, you can go low-budget. I have not tried this method, but it is supposed to be working. You will buy paracord, but in form of parachute string (it is really cheap, basically 9USD/30metres), cut the string a pull out the nylon core, so that you are left with the sleeving only. Then buy some industrial 16AWG/18AWG cable, but don't cheap out on connectors and terminals! :) You will then need some crimping tools and heatshrink (most people use black, but take my advice, go with transparent - so you can see when the sleeving starts melting). The process itself can be found on youtube... And not to forget, I got the combs from ebay (totally satisfied with those and saved considerable amount of money). https://www.ebay.com/itm/10pcs-Shakmods-Clear-Close-Cable-Comb-Set-2mm-3mm-or-4mm-Sleeved-Extension/172361838566?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649
Thank you for commenting and wish you good luck with your build!