Let me try and illustrate.
1. Arrive Krakow about 2pm. By the time you reach the hotel its 4pm. Walk, dinner, sleep. So why did you start here, well to save $800 on a drop off fee. But the day rental, the hotel, the gas, the time … all maybe close to $800.
2. Wake and eat breakfast and at 9am taxi to car rental company. 10am depart Krakow having seen nothing of Krakow. Drive time to Prague is 6:15, but there are any number of interesting stops along the way. For a list a good cheat is to go to Daytrip.com and put in the trip. They will offer you stops along the way, and you can get an idea of what’s worth seeing. Figure one stop of 90 minutes plus lunch, so now your trip is 8:45 and you arrive in Prague at 6:45 pm. Find a place to park the car, get checked in, clean up, then about 7:30 head out walk a bit and have dinner.
3. Today you get to see a city you have traveled to. Most spend 3 full days in Prague, you have one. Parking the unused car only cost 140 euro in Prague.
4. Wake, eat breakfast and hop in the car to Tihany on Lake Balaton at 9am. Since you will be driving right past Cesky Krumlov, that’s a logical stop for 2.5 hours with lunch. Probably worth 4 hours or even a full night but you have an 8 hour drive to finish. At 7:30pm arrive Tihany. Another hour to find your airbnb find a place to park your car and get cleaned up. Dinner and bed.
5. Today you have time to see the largest lake in Central Europe. Beautiful too. Or you can see Tihany, great place and maybe if you keep moving you can get to one winery. So “seeing some wineries” is seeing one … maybe.
6. After breakfast you head for Budapest. Will take you about 3 hours to reach Budapest, park the car and get to your hotel and check in. There are some interesting stops. Let’s say you find another winery on the way. Add 3 hours to the trip for that and lunch, so by 3pm you can start seeing Budapest. The unused car will only cost you 210 euro to park for three nights. You have 2.5 days to see the city. You know that’s not great, but its not insane either. You are one full day short of a good visit.
7. In Budapest
8. In Budapest
9. Back to Krakow. After breakfast. Start at 9am. The pretty drive is through Kosice and eastern Slovakia. Figure 6.5 hours but there are so many good stops, with slight detours, lets call it 9 hours or 10 with lunch. So arrive Krakow at 7pm, return car and check in, eat, sleep.
10. You finally have a day to see Krakow
11. Fly home.
My suggestion. Fly into Budapest for 5 nights and do some day trips. I know a guide that can take you to the wineries, introduce you to them. You can do 3 in a day. A few have wonderful accommodation for a night so you could make it an overnight trip and do some other sightseeing as well; like Tihany on the lake. Good guide. Then fly to Prague and do the same. If you wanted to add Krakow there is a night train out of Prague (regiojet) and I think an entire sleeping cabin is under 200 €. Just steal a night from Budapest and 2 nights from Prague.