Thank you!

is somewhere on the blockchain an entry like "post (link)" used up "123.123.123.123" RC?

I'm not sure if it's already possible, but I need to say, I didn't spend much time on calculating transaction costs yet. I know that they are still working on improvements for the RC API to enable other platforms and apps to receive such data in an easier way without having to calculate the values by themselves. In about two weeks from now I can tell you more ;)