Cookiebot on multisite network

Hi,
one of my clients has a multisite network made by 3rd level domains (each website is for a different location of his activity). The multisite consists of 18 webstites and the total amount of pages is about 6.000. Can I buy a single Premium Large plan or do I have to buy a small/medium plan for each website? Apart the relevant difference in terms of cost it will be complex to handle 18 licences.

Thanks,
Nicola