Isaiah 40:4…”Every valley shall be raised up, every mountain and hill made low; the rough ground shall become level, the rugged places a plain.” The idea of preparing the way of the LORD is a word picture including valleys, mountains, and hills, because the real preparation must take place in our hearts. Building a road is very much like the preparation God must do in our hearts. They are both expensive, they both must deal with many different problems and environments incapable of fixing themselves, and they both take an expert engineer.
Does the gospel you believe have any cost? The good news as outlined in the bible includes denying yourself:
Matthew 16:24-25Then Jesus said to his disciples, “Whoever wants to be my disciple must deny themselves and take up their cross and follow me. For whoever wants to save their life will lose it, but whoever loses their life for me will find it.”