That's a fair point.
It's a charge. You'd better be offering me at least the difference between the cost of mats and what the item I'm transmuting is worth on the AH. Preferably more.
If 60 Ghost Iron Bars are 300g, and Living Steel are 500g/bar (prices per my current AH), you'd better be offering me 200g for my cooldown, or I'm going to not-so-politely ask you to go stuff it. Because I could just go buy the ghost iron myself, use my own cooldown, and make that same profit off the AH, with the bonus chance of procs. Offering me less than the 200g for the cooldown means I'm losing money on the deal and the ONLY way that would be attractive is if I'm 1> too poor to afford 300g for the bars, and 2> don't have a farming alt.
In practice, I never end up using my cooldown for non-guildies, because people invariably have an issue with my rules, which I find hilarious, since they're literally asking me to lose money. "I know you can make 200g profit plus procs in a heartbeat, but you should TOTALLY take my 50g offer seriously, and I demand all the procs to boot". Yeah, no, you're an idiot if you're making that offer, and I'd be a sucker if I took it.
It's kind of like people spamming trade looking to sell Ghost Iron Bars for 200g/stack when there's 400 stacks on the AH at 100g/stack.