Sharing my experience:
I have had three bags dropped off at Hermes SF: a Kelly 32 Box, a Drag 27 Box, and a Kelly Sport GM Gulliver leather in Alezan.
The first two bags were both repaired in store, and I was quoted $315 each for basic cleaning/repair. I didn't really notice a huge improvement honestly because I still see visible scratches that were there before. The leather is a bit shiner, maybe it's all psychological who knows. So I'd say for the very basic service $315 quote you probably won't see a big difference. But I still recommend bringing in the bag to Hermes spa if said bag is purchased secondhand/vintage. It is just an extra layer of safety to bring peace of mind in terms of authenticity.
As for my Kelly Sport, she was in a worse condition compared to the previous two and got sent to Paris for repair instead. Needless to say it was a very very long wait (about 3 months) until I heard back about the quote. I was quoted $430 for side strap replacement and $800 for shoulder strap replacement. Cleaning is free this time, but no guarantee of restoring to original condition. I anticipate another few months at least before the bag gets shipped back to the US, but hopefully I will be able to notice some difference this time..