How far a day reaches
Mtskheta is 20 kilometres north, 25 to 30 minutes off-peak, and works as an afternoon rather than a day. Kazbegi is 157 kilometres north, three to three and a half hours each way without stops. Borjomi is 165 kilometres south-west, two hours 15 to two hours 30 each way. Kutaisi is 220 kilometres west on the S1, three and a half hours each way and a long day by any measure.
What a day costs
A full day runs 8 to 9 hours. The S-Class is 1 500 ₾, the V-Class 1 350 ₾ for up to seven, and the Maybach 2 500 ₾. Longer days are charged by the extra hour rather than re-quoted. A half day is billed hourly instead: 200 ₾ for the S-Class or V-Class, 300 ₾ for the Maybach, with a three-hour minimum.
Half a day in the city
Not every day has to leave Tbilisi. The old town, the sulfur baths, and the hours between two meetings are all half-day work on the same hourly rate. The route is quoted by time rather than by stop, so it can change while you are in it.