On another note do we have an estimation of how many players would go back to sell their crafted items if undercutting bots were not a thing anymore, and what would be the consequences of it ?

Actually we are in a situation where the prices on some items becomes always lower, and where legit crafters trying to sell them become pissed off being undercut all the time, because a few bots have the monopoly on these items. But if these few bots were gone, wouldn't they be replaced by a lot of crafters not cheating ? If there is too much of them, the prices will stay the same, and the exasperation about undercutted every few minutes will stay the same as well. Because instead of being undercutted by the same bot every 15 minutes, you will then become undercutted by player A at +8 minutes after having put your items on sale, then player B at +13 minutes, player C at +21 minutes, player D at +32 minutes, etc.

With even the risk of A, B, C, or D undercutting not by 1 gil only, but like 20% of the price to sell their items faster, because they are impatient humans and not a bot programmed to always use the same price reduction. Except that E, F end G will then follow the 20% decrease, making the prices drop even faster.

While the bots are for sure a problem that needs to get rid of since what they are doing is forbidden by the TOS, i am not sure that you should expect to suddenly become rich and not being undercutted all the time if they were not around anymore. Especially since the gathering and crafting rework, which made all the crafted items way easier to make, and the competition way bigger than before.