Krumlov is not a cheap town - it is a UNESCO site of 13,000 people with a single tourist season - and what controls your budget is how much of the castle you pay to go inside.
The castle museum and tower are the cheap ticket
The guided interior routes need a timed slot and a guide. The castle museum and tower are self-guided and open daily 09:00-16:30 from September to the end of October, then Tuesday to Sunday 09:00-15:30 until 20 December, which is the cheapest way to get up the painted tower.
The castle gardens cost nothing
Terraced, free and open 07:00-19:00 daily from 1 May to 30 September and 07:00-17:00 through October. They close for the winter on 1 November, which removes the town's best free hour from the itinerary for half the year.
The Regional Museum is the 60 Kc hour
Horni 152, Tuesday to Sunday 09:00-12:00 and 12:30-17:00. Sixty crowns for adults, thirty reduced, a hundred for a family - and its ceramic model of the town around 1800 explains the street plan faster than any walking tour.
Come by bus, and come off-season if you can
The train means changing at Ceske Budejovice onto a slow branch line, so the practical approach from Prague is the coach, which sets you down at the bus station on the edge of the old town and leaves you a short walk downhill. Beds and restaurant tables are easiest to get outside July and August.
What a day costs
The Regional Museum is 60 Kc, the gardens and the lanes are free, and the graphite mine - the one big-ticket item outside the castle - is 250 Kc, or 650 Kc for a family. Do the tower, the museum and the gardens and you have spent under 300 Kc on sights; the bed and the dinner are what push a Krumlov day over a Brno one.