Most cruise packages include transfers to and from Hanoi and you can get really cheap cruises beginning at a rock-bottom jaw-dropping 30 USD per person to do an afternoon cruise around the bay and going upwards to 400 USD per person/day for a luxury overnight cruise. You do not need to book with a luxury operator to have a nice cruise, but if you book at the budget level it is hard to know what to expect in terms of service, food, safety, and accommodations. The budget tours are often booked through travel agents who place people with different tour operators and boats in order to adequately fill up as many spaces as possible, so you really may not have a good idea of what things will be like until you get aboard. And for to help you imagine clearlier, only the entrance fees during  a cruise trip cost about 21 USD, so with 30 USD price, which can of food, accomadation and activities they will give you to still make profit? Discover Halong believes that you already have your answer.