WTF is an open API? An API that allows you to use it?

What good would a closed API be that you can't access?

Indeed looks like they're after some organic traffic.

Similar shenanigans with other freemium products, where the bare minimum is free, but makes you dependent on shopping for the costly features.

It's extremely hard. To compare pricing, especially with concurrent users etc. I have to say, adobe is one of the most transparent in that regard, it's very clear what you will get.