What you'll find is that as features and reporting and business user-friendly UI becomes more important, there's overhead that comes with the company to provide

What you'll find is that as features and reporting and business user-friendly UI becomes more important, there's overhead that comes with the company to provide those things, so their CPMs (or other pricing) tends to go up. SES is for all intents and purposes a "dumb pipe" that will send email, and provide APIs for things. AWS Pinpoint is a step up from that, but I personally found some features lacking at this point aside from basic usage compared against more full-featured ESPs. There's a whole range of products catering to different market segments though. Mailchimp is what I'd consider more in the SMB tier in many ways, and then you go all the way up to things like ExactTarget, Responsys, etc. at the Enterprise level. Even then there's considerations around pricing models that depends on whether you're more of a low-volume, high-touch B2B business, or high-volume B2C for example. Definitely helpful to demo several providers and compare them against a business/technical needs assessment matrix, of which pricing is probably just one factor (and perhaps not even the most important).