I'm not rlly that aware of how boring works, so I'll take ur word for it there I suppose.
Any moon mining is going to be expensive because it's the moon. That kind of travel is going to be expensive.
For this tho, u don't have to "travel" anywhere. U just build a one time installation on the moon, which would be expensive. Once it's built, u just launch stuff from the moon using a railgun like system with enough velocity to deorbit it, use the earth's atmosphere to slow down enough that the material doesn't vaporize on a crash landing in a designated location. This would most likely be how we would get our material in the future.
Whose cost would be energy and light wear and tear on the railgun. Which won't be much at all.
(I thought by "travel", u meant having to use spaceships to transport material which would be significantly more expensive).