I was selling loot to TT but repairing A106 was on my todo list also. I forgot to switch terminals and tted my amp. It was tt+1400 back then so I took their deal, 1000ped fee for my amp back. But I wouldn't call it "voluntary processing fee" nor fair. How can you explain 1000ped fee when withdrawal has only 100ped? It's a penalty and extra income source for MA. And it's not time consuming - when I sent my support case then got back to me after less than 20 minutes confirming they saw my transaction in logs. Restoring sold item is a matter of minutes, not hours or days so $100 is too high if you ask me. I told them I play 10 years and it's first time it happened to me so would be great if they could lift that fee for me first time - but they didn't care apparently.
Anyway I did more or less what you predicted - my trust in them was the lowest it ever been and I decided to make a little boycott. I didn't quit but I lowered my activity level, instead of hunting as I always did, I traded my way out of that fee. I track my hunting returns very very carefully and I can tell the time I committed to gain that 1kped back trading - I would lose around 3kped (and get it back in MU but that's another story

). So at the end I lost nothing in PED - only some experience I would get hunting. MA gained 1kped due to my mistake but lost 3kped due to my break in hunting. That's the example of penny wise and pound foolish
