I have been known to pay for various crafts from time to time if I cannot find someone I know to do it for me. Personally, I wouldn't pay more than 10k due to the reasons Konoko stated: doesn't take much out of a crafter's day.
As for my cluster, my crafter and THF farming buddy was one in the same, so I did give him a reward for the time he put into the effort.
A reward offered in a WG shout, to me, is nothing more than an attention grabber/enticement because we all know that it's not the easiest of tasks trying to get a stranger to do something for nothing in our self-serving community.