3D models for Race Track Builder - Xpackers

Hi,

I'm creating a racetrack through Race Track Builder for Assetto Corsa.
I would like to add unique objects to it like:

- Advertising billboards (string objects trackside) and hanging advertising billboards like in the attached picture, to which the sponsor/image attached can be changed.
- Kerbs with specific sets of colors
- Grand Stands
- Pit Buildings
- Building and monuments from a specific city

I would need as an output the blender file, ready to be exported to .fbx so it works into the Xpacker creator and in Racetrack Builder.

I would like to understand the cost of each item.

Some tutorials to understand details:
https://www.youtube.com/watch?v=nYti6Np6j3Q&t=251s
https://www.youtube.com/watch?v=G3uA_zJyepE&t=207s
https://www.youtube.com/watch?v=AcMqGQGUZkA&t=883s
https://www.youtube.com/watch?v=gAUpS6kjCeM&t=1080s

Thanks.
Marco