Mailchimp's pricing really doesn't seem all that outrageous to me - considering the time you state it saves
There are some industries like Game Development where only one or two emails are sent to the entire distribution list per year.
If you're collecting emails on game announcement at month 0, and releasing at month 24, for an average Indie game at $14.99, deducting 30% platform commission, Mailchimp costs alone represent 2.1% of your net revenue per customer - pretty extreme.
But yes, some people are happy to personally pay the costs for others to enjoy their services.
Any organization with a list that large should also be able to raise enough funds to cover the cost of hosting.