As a former customer (it has admittedly been a few years) I'm not surprised. Sendgrid's entire business is based on price. Emails are one of the few costs that don't really scale that well. They cost a lot more than people think they should. When I list did a cost analysis they beat out a lot of other providers.

I haven't used them in years, so I'm not sure if they are still the low cost leader, but they are definitely the kind of thing where you get what you pay for. Their lack of investment in product and infrastructure showed for the years I used them, and their slowness in delivering updates was incredibly frustrating.