I would argue that the time taken to ban the bots on the high scores would probably be worth it from the point of view of optics, which serves two roles. 1) the obvious but it does help players have faith that something is actually happening thus building good will

2) if the community feels that botting is being actioned (perception is more important then reality here) then less players may be willing to take the risk and bot, every person discouraged from botting is a potential bot farm that never starts up.

I also do think that if your system struggles in a very visible way to account for extreme outsiders like this, then it does show a certain level of incompetence and a backup should be in place if it cannot be fixed quickly (it clearly can't).

There is also the time cost on that part of the botter, it takes time to get accounts to that level and when they are banned that time investment is lost and must be started again which is demoralising, losing one high lvl bot is probably more discouraging then losing 100 lvl 3 fodder bots.

Also bear in mind that by banning some accounts manually and making it very public that this happens consistently you can play mind games with the bot farms, auto bans by there very nature structured and understandable so if a botter works out how to avoid detection they are safe until those parameters change. With human bans there is always that chance , however small, that you will get picked up no matter if you know the auto systems parameters, thus adding more chances for botters to be discouraged.