Strange buy out of items

[Xystic]

To the original post this is a common tactic to artificially raise prices. They flood the history so you can't tell that the previous price was pittance in comparison.

This is precisely correct. Its a common tactic used to drive prices up. It has nothing to do with bots.

Bots in general, buy the cheapest of the items. They aren't going to dump that much gil. If someone is buying it for high prices, they are bumping up the value of items themselves. You pay a small amount but you bring the overall value of the item up and if you have a huge supply, you can technically now increase your overall gain.