30-50k is a huge number for sending blackhat emails on a daily basis.
To break it down to send 50k emails a day, you would need the below infrastructure:
Domains: 400
Mailboxes: 2000
Total sends per day per mailbox: 25
Cost of cold email tool (approx): 500-800$ per month odd.
Cost of domains: 400*10$=$4,000.00
Cost of Mailservers: for 2000 mailboxes - 600$
i would recommend 4-5 different servers. Each mailserver would cost you around 150$ per year i.e, 600$ per year. (If IP gets blacklisted, have atleast 2 backup servers getting warmed up )
So you are looking to spend atleast 600$+4000$+500-800$ - think over if you want to send that email volume and if it would be profitable. If everything checks out, go right ahead with the setup. I will provide more info wherever you are caught up.