Chitwan is cheap to sleep in and expensive to enter: the daily park permit and the per-vehicle price of jeeps and canoes are what actually set your budget, not your room.
The park permit
Chitwan National Park charges foreigners NPR 2,000 per person per entry, SAARC nationals NPR 1,000 and Nepalis NPR 150, with under-10s free. You pay it for every day you go in, so plan which days you actually enter rather than buying reflexively.
Tourist bus in, not night bus
Daily coaches from Kathmandu and Pokhara reach Sauraha in about six hours for roughly NPR 700-1,200. Take the morning departure — the night services on this road are not worth the saving.
Share the boat, share the jeep
Canoes and jeeps are priced per boat and per vehicle, so the cost per head collapses if you fill them. A dugout canoe on the Rapti paired with a guided walk back runs about NPR 1,400-1,800 and is the cheapest way into the park once you have the permit.
Monsoon is cheap for a reason
June to September brings the lowest room rates of the year along with heat, humidity, leeches and partial flooding, and some activities stop entirely. October to March costs more and is when the wildlife actually gathers at the waterholes.
What a day costs
A day in Sauraha without entering the park — budget room, two dal bhats, a bike, a beer at sunset — sits in the low thousands of rupees. A park day adds the NPR 2,000 permit plus your share of a jeep or the NPR 1,400-1,800 canoe-and-walk, so plan on roughly double for every day you go in.