All white rods up to oak (tier IV) are worth 1 fg. Some people may pay a little more for perfect or near-perfect durability. I wouldn’t because they’re so common and if you break one just get another.
Plain rods tier V to VII-ish are worth 1-5 fg. After that, the price may slowly rise.
Rods tier X and up “should” be worth 20+ IMO but there aren’t many fishers on HC who are able to fish at that high level, so... good luck selling high lvl rods.
Rods with a lot of durability (100 or more): prices really fluctuate. The reason is because, like I said, not many fishermen. Also, if you lag, bye bye rod. So it’s a very bad investment. I haven’t seen anybody offer even 100 fg on any rod in the years I’ve been here.