It is illegal if the website’s TOS for making a purchase prohibits the use of automated software.
It doesn't matter if it's legal, it matters if the website owner doesn't want x doing y on their site. A bot consistently not abiding by owners' intent is inheritly malicious.
It doesn't matter if it's legal, it matters if the website owner doesn't want x doing y on their site. A bot consistently not abiding by owners' intent is inheritly malicious.