From google searching on this, it seems MB bots are far less publicly available than gathering or combat bots. Probably the main reason is because releasing it to the public is impractical, for example 2 or more bots competing and the fact that for the average player it's just not worth camping a MB for tiny profit and grinding prices into the dust when your bot could be out gathering or gil farming. The usual ff14 bots won't add the feature. MB bots do seem to exist, but they're created and sold by commission, or used by, private developers.

I find that sort of thing rather interesting, but it's very disturbing how much of a botting community there is. I think the biggest issues for prices are gathering bots creating massive supply and the fact crafting is just far too easy now, with demand at an all time low since there are ten times more sellers, but far less buyers since more people can just make their own.