calculation of 3D-animation, costs of 3D-visualisation


sometimes have the chance to make some money with blender. However I am mostly quite unsure what costs I should tell the client in the offer.
I can think about complexity in geometry, texturing, existing usable CAD data, animation efforts (particles are critical I think), length of the animation or still and so on. Breaking it down to a houry rate is difficult for me, sometimes I try and then have to rebuild someting…
Have you got tipps about cost calculation or can you point me to informations or project examples to see how much an animation like xyz costs? Do you know a webpage or book (english or german)?
(In my current case these are technical visualisations, not too detailed or photorealistic but yet looking nice for advertising and explanation purposes. I will have something looking like fluid in it and particles.)

Would be so great

Thank you, the link is helpfull.