1. Access: Can we get material close, or are we hiking it in?
  2. Stone: small river rock vs. huge statement boulders is a different universe.
  3. Elevation & length: more drop and more stream equals more labor and rock.
  4. Filtration & plumbing: koi-grade systems cost more, but they work better.
  5. Electrical & lighting: transformers, wiring runs, and fixture count add up.