Details: http://mailchimp.com/pricing/high-volume/
Mailchimp is thus $475.00 per 100K per month ($5700 per year!) That is a lot to spend on just email.
With Sendy + SES it costs me $10 to do a send to our 100,000 users.
Now I could play around with switching plans all the time at MailChimp to try and always minimize my costs, but I don't want to play that game. SES + Sendy keeps my costs linear with the number of emails I send, I don't have to play any games with changing plans, and it is significantly cheaper that MailChimp.
Or, as noted throughout this thread, just use SES (or Mandrill if SES's deliverability scares you, but IMO it shouldn't).
Amazon SES also has very good IPs. If you check them on https://senderscore.org you will see they usually rank above 95%. The only problem is Amazon SES strict policy against bounces and complaints. So your list has to be very clean and ideally double opt-in before you can send. Also Amazon SES starts you out with 10k emails/day and 5emails/sec. You need to ask for a quota increase (which was always granted in my experience) before sending higher volume faster.
My tip: If you have some old/invalid emails that you know will cause problems with Amazon SES, send to your most active (recent openers and clickers) first and then gradually introduce your older emails. Monitor your bounce and complaint rates to stay below 5% and 0.1% respectively.