150 USD/month for a family of 3 is a quite modest number for me, it's really a very low standard of living compared to the standard of living in my country. My family consists of 4 people, every month I have to spend about 400$-500$ and we are a poor family, belonging to the low-income class in my hometown. I am actually quite surprised with the level of spending in Bangladesh, it is so different from my country while my country is not richer than Bangladesh.
Well, everything depends. As I said, sometimes $500 for two people is too low an amount if you live in a city, you have to pay for the rent as well. However, most Bangladeshi have their own house in the village, and vegetables, fish, and rice are the main foods for Bangladeshi people. Maybe $150 is too low, but if they spend $200 for three people and they live in a village side, it's good enough. Because most Bangladeshi people have land to firm vegetables and Rice, it's not below standard. You can live like a king in some places with $200-$250 monthly. But everything is changing these days. There was a time when $100 was enough for a family in Bangladesh, and it's not too long ago.