Only Twitter will know that the 10,000 accounts are bots. It'd be up to them to ban, but why would they ever ban a high-paying customer who is paying literally 10,000x more than the typical user?
the change is to require payment for all new users so they won't be paying more than anyone else other than the old accounts that got grandfathered in. They won't ban them if they pay but they will derank their posts and if they do allow a group of them to sign up with the same CC then they can punish the entire block of them if they start spamming with any of the accounts. It also allows for permabans based on CC or other identifying info making it more difficult to create a new botnet. It's not a perfect solution but it does add friction. There will probably be ongoing changes to make it even harder for bot accounts.