Ok, thx and nvmLook at this video u'll understand better how VFX works I don't know if ILM works different but usually they have a contract for X amount of money
https://www.youtube.com/watch?v=TgSPys9PatU
For the stuff that they've built it's different you don't know exactly how much it'll cost you have models then test materials colors and so on so it can be much expensive not cheaper
I don't think you can find the exact numbers