Hey love the work you guys did on the UI kit looks great!
I would personally pay upwards of $120 for this given how many hours went into making it and how much time it would save me.
With a higher price you can limit the number of initial developers to the ones where this kit meets a majority of their needs. If you price it too low you will bring in much more noise from a long tail of developers who will ask for a much wider range of features and spread your effort thin. I think for the first few weeks/months you want to hone the product to meet the expectations of the higher paying developers rather than try to go after more revenue with a lower price. I think 10 great and serious developers at $100 is better than 100 hobbyist developers at $10 for the initial stages of this kit. Over time you can lower the price when you are ready to expand the features.