A RG80 should be around $90k give or take. If you’re not in a territory you can shop it more easily.
Your time on stumps meaning 6 vs 10 minutes? Yes. I’ve got way more experience grinding than the guy that runs our SG75. I am not nearly as familiar with the SG75 as I am Raycos (bought an RG50 in 1998).
That being said, given the choice, me running the RG80 gets the job done in a third to a half less time.
The RG165 is pushing 2x as fast as the RG80 in bigger stumps, both running Green Teeth. The 1100s on the 165 can pull some massive chips; it’s great. The 165 is something like 3x faster than the SG75, although they haven’t been on the same job yet, and probably won’t be.