The number one item to buy in Dhaka is fresh water pearls.
I paid 1,800 Taka ($21) for five strands of pearls. Apparently, you can test if they are real by rubbing the pearl against your tooth to feel for sandy texture. Or you can set flame to he pearl. I did neither of these things. I figure that it looked nice, the salesman was good at his job, and he strung those pearls up in a flash. You can ask for a knot to be tied between each pearl if you want them to be more secure (the end of the string is melted into the clasp), but you have to ask.