score:1
I got an answer from the tour operator:
Though we pay a good salary to our staff, clients usually tip them for their good job. Generally on a tour for 2 persons they tip minimum US$ 20 - $25 total per day for the guide and about $15 - $20 total per day for the driver. However, it is upon you to add more or pay less.
It is nevertheless quite unclear.
Upvote:1
While I've never been to georgia, when I was touring eastern europe with friends, we usually tipped all our drivers 5% - 10%. Depending on where you're travelling from, if you can afford to let go of a few coins then whether it's customary or not, it's a good idea.