Quick answer: Ho Chi Minh City runs about EUR 45 per day mid-range - noticeably less if you eat local and walk. Cheapest window: December-March - dry season with lower humidity; avoid the heaviest rains of June-September.
What things actually cost
bowl of pho
2 EUR
ca phe sua da
1.20 EUR
banh mi at a stall
1.50 EUR
Grab bike across District 1
1 EUR
local beer (Saigon)
0.80 EUR
War Remnants Museum entry
1.50 EUR
Eat well for little
Pho at Pho Le or Pho Hoa - beef noodle soup done properly, about 2 EUR
Banh mi from Banh Mi Huynh Hoa - the famous stacked version, about 2.50 EUR
Com tam (broken rice with grilled pork) at a street stall - about 2 EUR
Ca phe sua da (iced milk coffee) at an old apartment cafe - 1 to 1.50 EUR
Banh xeo (crispy pancake) at Banh Xeo 46A - about 3 EUR
Money mistakes to avoid
Hailing random taxis and getting rigged meters - use the Grab app for cars and bikes instead
Holding your phone loosely at the curb - bag and phone snatching from motorbikes happens, keep them on the inside
Freezing at street crossings - walk slowly and steadily, traffic flows around you; stopping mid-street is what causes problems
Booking a full-day Cu Chi tour when a morning trip is enough - the site takes 2-3 hours, go early to beat heat and crowds
Transport without the tourist tax
From Tan Son Nhat Airport a Grab car to District 1 costs about 5-7 EUR and takes 30-45 minutes; bus 109 is under 1 EUR. In town, Grab bikes (under 1.50 EUR per hop) are the fastest way around.