This, dns4.pro is awesome, @Amitz is behind this project for anyone curious. Very simple and just works.Protip; dns4.pro
Correct, I believe it isDomains are free... They don't charge for adding domains (I think).
Queries are free up to 250k per domain. (i.e. you can add x domains and each have 50k queries and your monthly bill would be $0).
Queries after that are billed at 1 million intervals.
The amount for each 1 million queries is 1.50 euros.
If you are paying 16 euros a month you are in the territory to consider partner promo pricing:
15EUR/month for each 85 domains (regular offer 15EUR/month for each 75 domains)