How to price new project ?

Hi i would like to start a project but dont know how to price it. I need SLS rocket parts like that:

with quality like on this clip:

https://www.youtube.com/watch?v=XcPtQYalkcs&featur...

It ment to be use as game asset but author will be able to sell models however he wants.

If i want to start a project i need to post a value. I dont want to post 50$ coz its too low but I wont pay 2000$ as well so how can i resonably evaluate the project like that if it contains 13 3D models of different difficulty lvl ? This is ment to be use in Unity 3D game.

Any tips ?

Thx.