From https://ello.co/wtf/post/about-ello :
Ello is completely free to use.
We occasionally offer special features to our users. If we create a special feature that you really like, you may choose to support Ello by paying a very small amount of money to add that feature to your Ello account.
You never have to pay anything, and you can keep using Ello forever, for free. By choosing to buy a feature now and then for a very small amount of money you support our work and help us make Ello better and better.
Aww yiss, I am no longer the product! SHUT UP AND TAKE MY MONEY!! :)