Need help valuing high-end power cables.

I’m looking for help in valuing a lot of 5 Synergistic Research power cables. 
Here’s the backstory. I am doing this to help a ~75-year old friend, who has been operating an electronics repair shop for 40+ years. We live in a rural area in the mountains of North Carolina, and this fine man is struggling to keep his doors open. He is a wealth of knowledge, a true community asset, and I cannot imagine my small town without him or his shop.

These cables were given to him by a “good long-time customer” who himself is a retired audio engineer from a VERY high-end stereo company, which I think it best not to name. He told my friend the shop owner that he never used them, and to me their condition looks to be excellent. A few of them are labeled “Demonstration - Not for Sale.”

My friend has had these laying around his shop for about a year, and I have drooled over them; but know they are out of my system’s league, my price range, and all my vintage gear has the power cables built-in anyway.  He doesn’t have the Internet savvy, or the patience frankly, to sell these online. I am going to try to sell them for him, as a favor, because I know he could use the money, and I hope he can continue in his business for a long, long time.  

Here’s the help I’m requesting. I’ve done some research, and I really have no idea how to price this lot of five cables. I don’t want to sell them individually, I just want to do a single sale.  If anyone can suggest a fair private-sale price range, and/or offer any advice for how to market/package/sell these I would be very grateful.  The goal is a quick sale, thus the buyer gets a good and fair deal. 

So, here is the lot. All five cables look to be in Mint or Near-Mint condition.  Each comes with its own power supply.  All five cables are Synergistic Research brand. 
1. One Tesla S.E. Hologram D (a monster)
2. Two Tesla Series Tesla T3
3. Two Tesla Series Tesla T2

If someone from this forum were to want to buy them, I would list them on this site, and not circumvent Audiogon’s business model. Thank you to the board for your input and help.  I have learned a lot from this crew over the past year.

FYI my two systems:
Matching Sansui AU/TU 5900 integrated and tuner, Dual CS-5000 TT w/Ortofon cart, Raspberry Pi 4 Volumio w/DAC hat, Paradigm SE-1 speakers, cables are quality but basic.

Matching Kenwood KA/KT 3500 integrated and tuner, Dual CS-5000 TT W/Grado cart, Paradigm Reference Studio 40 speakers, cables are quality but basic.

Regards.