When hiring a car and driver, the private and custom tour is charged per car not per person. Therefore, if you come in a big group of family and friends, you can share the costs.
For example, this Toyota Commuter 2020 has 13 seats plus 1 seat for a driver. 8-hour Kyoto Tour costs around ¥80,000 Inclusions are tax, car, driver, toll fees, fuel fees, parking fees, tour management, hotel pick-up and drop-off.
If you come in a group of 13 people, 1 person will cost only ¥6,153 (which is less than $50 with the current exchange rate).
If you need a private tour guide (plus about ¥40,000 for 8-hour tour), the total cost would be ¥120,000. The remaining seats for your group would be 12 people. Then it will cost ¥10,000 per person which is less than $80 with the current exchange rate.
I hope this article helps you to plan your trip to Japan.