I love this metric. It was very fun to build and optimize, and I'm very proud of my solution. I still only have 40 hours in the game, 20 of which were spent on this single puzzle, but the campaign seems quite boring now compared to this. After my initial solution for width 2.5, I managed to save single bits of track here and there and broke the 200 cost barrier. My original layout had both input and output at the bottom, and the combinator at the top. I tunnel visioned on this layout and managed to bring it down to 180g, which I deemed unbeatable. So on Thursday, I considered other possible layouts and noticed you can just put the combinator in the middle and work around it with two pistons. I found an arrangement that works and brought my cost down to 165g!! Finally, on Friday, I cut out one last piece of track, leaving just four behind. I wrote this a lot of times before, but now I actually don't know how to realistically improve this. I'm hopeful for top 50, but you never know with this community :3
PS: Shoutout to the online editor Omclone, it was a game changer
PPS: You misspelled the puzzle file name