Don’t worry about basic features being charged for, I’d nip that in the butt pretty quickly and I’ll tel you how. I’ll be making custom Brics for very simple tasks as well, such as mail chimp and I’d make them completely free.
However, we as a company also have plans for Brics that we will charge extra for. Right now, I don’t want to charge yearly for Blocs, push the price too high because the app becomes more pro and I don’t want to fragment the pricing model with various versions, but I do want to add BIG features at an additional cost somehow because that’s how Blocs will survive. For example, Pinegrow offer a wordpress version of their app, rather than do that, we would offer Wordpress Brics and additional export features and charge separately for them, I personally feel this works better. Because the user who wants Wordpress pays extra and the user who doesn’t isn’t forced too.
So to summarise, I think the API will offer both, paid Brics and free ones, I don’t think charging for basic API tap in Brics will have a leg to stand on because I or someone else (blocsusers-free-custom-Brics.com 
) will just implement those and dish them out free. However, there will be much more advanced Brics too that will come at a price. It’ll be no different to any other Developer community, Wordpress, Sketch, Photoshop, Shopify. They all offer products made by 3rd parties, many free and some at a price.
One thing is for certain there will be a lot more free Brics than premium ones. I personally like to pay, because I like to get some form of support. Not everyone will offer support for free Brics.