Hello,
Thanks for your reply.
Yes, there is no additional charge for generating a new key for your new site.
If you are using a single site license, then you would just need to delete the old key and generate a new one, but if you are using a license for unlimited sites, then you can generate as many keys as you want for your websites.
I hope it helps. Please contact us if you have any more queries.
Best regards,
Moshtafizur