If domains and IPs get blacklisted (it doesn't even have to be blacklisted but just marked as spam by recipients) off course you have to setup all new to be able to reach inbox again (inbox of the most used mail providers like gmail, outlook, yahoo etc.)
Cost for 1M emails per month depends on what you want to do.
If you have own email list from your subscribers and they expect to receive emails from you (newsletters) than it can be very cheap.
In this case you need one or two VPS cost ~︀ $80 month + domain + email marketing app (there are free ones) + cost for︁ admin who will set up all for you (Configure Linux box with web service, sql︂ service and mail service and all dns stuff needed for 10/10 mail test) ~ $200︃
If you want to send "spam" to send e-mail to million random e-mails addresses and︄ stay in inbox you need match complicated set up.
1 powerfull VPS for EMS ~︅ $120 per month
1 powerfull VPS for MTA mangement ~ $120 per month
multiple domains︆
multiple cheap VPS for SMTP senders / 1 cheap VPS with 3-5 IP addresses ~︇ $15
EMS recommended app Mumara ~ $1500 but can be found cracked
PowerMTA ~ $5500︈ but can be found cracked
Admin to set up whole system ~ $2000 one time,︉ depends on number of servers + monthly cost for maintains
This set up can easily︊ send 1M emails per hour but you will ruin it after few days and forget︋ about inbox.
But with good strategy and reasonable volume per day you can reach 1M︌ for 30 days.
Volume calculation, recommended starting sending about 5,000 messages per day from each︍ IP address to each ISP so you can calculate how many smtp vps servers you︎ need.